Introduction
Abdullah ibn Mas'ud began life as a young shepherd in Mecca, working for a man of Quraysh, with no status or wealth to his name. He accepted Islam very early, among the first handful of believers, and was among the earliest to recite the Quran openly in Mecca, even at the cost of a beating from the Quraysh.
After the migration to Medina he stayed close to the Prophet, serving him, carrying his sandals and water for wudu, and learning directly from him. The Prophet described him as a reciter of the highest rank and named him first among the four people the Ummah should learn the Quran from. He narrated a large number of hadith and became one of the great jurists among the Companions.
In later years he was sent to Kufa to teach, where his students (such as Alqama and Masruq) carried his understanding of Quran and fiqh into the generations after him. His life shows what a lowly start, sincere devotion to the Book of Allah, and a habit of humble, careful teaching can grow into.
The story
Mecca, early Islam (c. 610s CE)
Accepted Islam among the very first believers and was known as a young shepherd before it.
Mecca
Recited the Quran aloud in front of Quraysh, in the early days of the call, and was struck for it.
Badr, 2 AH / 624 CE
Present at Badr; sent by the Prophet to look for Abu Jahl on the battlefield and found him fatally wounded.
Read the wording
Sahih al-Bukhari 3963Sahih Arabic text
قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم يَوْمَ بَدْرٍ " مَنْ يَنْظُرُ مَا فَعَلَ أَبُو جَهْلٍ". فَانْطَلَقَ ابْنُ مَسْعُودٍ، فَوَجَدَهُ قَدْ ضَرَبَهُ ابْنَا عَفْرَاءَ حَتَّى بَرَدَ، فَأَخَذَ بِلِحْيَتِهِ فَقَالَ أَنْتَ أَبَا جَهْلٍ قَالَ وَهَلْ فَوْقَ رَجُلٍ قَتَلَهُ قَوْمُهُ أَوْ قَالَ قَتَلْتُمُوهُ
“Ibn Mas`ud went and found that the two sons of 'Afra had struck him fatally”
Medina period
Taught by the Prophet directly, including the surahs and the tashahhud of prayer.
Read the wording
Sahih al-Bukhari 6265Sahih Arabic text
… سَمِعْتُ مُجَاهِدًا، يَقُولُ حَدَّثَنِي عَبْدُ اللَّهِ بْنُ سَخْبَرَةَ أَبُو مَعْمَرٍ، قَالَ سَمِعْتُ ابْنَ مَسْعُودٍ، يَقُولُ عَلَّمَنِي رَسُولُ اللَّهِ صلى الله عليه وسلم وَكَفِّي بَيْنَ كَفَّيْهِ التَّشَهُّدَ، كَمَا يُعَلِّمُنِي السُّورَةَ مِنَ الْقُرْآنِ التَّحِيَّاتُ لِلَّهِ وَالصَّلَوَاتُ وَالطَّيِّبَاتُ، السَّلاَمُ عَلَيْكَ أَيُّهَا النَّبِيُّ وَرَحْمَةُ اللَّهِ وَبَرَكَاتُهُ، …
“taught me the Tashah-hud as he taught me a Sura from the Qur'an”
Caliphate of Umar and Uthman
Sent to Kufa as a teacher and treasurer, and became the teacher of its first generation of jurists.
c. 32 AH / 653 CE
Died in Medina and was buried in al-Baqi.
A day in their footsteps
9 small, repeatable practices from Abdullah ibn Mas'ud's life. Each comes with the Arabic text and English wording of its source, and links to read the full report.
Reciting the Quran to others, and listening
Ibn Mas'ud recited Surat an-Nisa to the Prophet when asked, at the Prophet's own request, and reached the verse that made the Prophet weep. He also had students recite to him and listened carefully, correcting where needed.
Try this today
Set aside time each week to recite to someone or listen to someone else recite, and let the verses move you.
Sit with this
When did someone last recite to you, or listen to you recite?
Sources
Sahih al-Bukhari 5050Sahih قَالَ قَالَ لِي النَّبِيُّ صلى الله عليه وسلم" اقْرَأْ عَلَىَّ". قُلْتُ يَا رَسُولَ اللَّهِ آقْرَأُ عَلَيْكَ وَعَلَيْكَ أُنْزِلَ قَالَ" نَعَمْ". فَقَرَأْتُ سُورَةَ النِّسَاءِ حَتَّى أَتَيْتُ إِلَى هَذِهِ الآيَةِ{فَكَيْفَ إِذَا جِئْنَا مِنْ كُلِّ أُمَّةٍ بِشَهِيدٍ وَجِئْنَا بِكَ عَلَى هَؤُلاَءِ شَهِيدًا} قَالَ" حَسْبُكَ الآنَ". فَالْتَفَتُّ إِلَيْهِ فَإِذَا عَيْنَاهُ تَذْرِفَانِ.
“Recite (the Qur'an) to me.”
Sahih al-Bukhari 4391Sahih … أَمَا إِنَّكَ لَوْ شِئْتَ أَمَرْتُ بَعْضَهُمْ يَقْرَأُ عَلَيْكَ قَالَ أَجَلْ. قَالَ اقْرَأْ يَا عَلْقَمَةُ. فَقَالَ زَيْدُ بْنُ حُدَيْرٍ أَخُو زِيَادِ بْنِ حُدَيْرٍ أَتَأْمُرُ عَلْقَمَةَ أَنْ يَقْرَأَ وَلَيْسَ بِأَقْرَئِنَا قَالَ أَمَا إِنَّكَ إِنْ شِئْتَ أَخْبَرْتُكَ بِمَا قَالَ النَّبِيُّ صلى الله عليه وسلم فِي قَوْمِكَ وَقَوْمِهِ. فَقَرَأْتُ خَمْسِينَ آيَةً مِنْ سُورَةِ مَرْيَمَ، فَقَالَ …
“Recite, O 'Alqama!”
Learning when and why each verse was revealed
He was known to study the Quran with its setting and context in mind, and said that no surah was revealed that he did not know where, and no verse that he did not know about whom.
Try this today
When you read a verse, look up its context too, so you read it as it was first understood.
Sit with this
Do you know where and why the verses you love were revealed?
Source
Sahih al-Bukhari 5002Sahih قَالَ قَالَ عَبْدُ اللَّهِ ـ رضى الله عنه ـ وَاللَّهِ الَّذِي لاَ إِلَهَ غَيْرُهُ مَا أُنْزِلَتْ سُورَةٌ مِنْ كِتَابِ اللَّهِ إِلاَّ أَنَا أَعْلَمُ أَيْنَ أُنْزِلَتْ وَلاَ أُنْزِلَتْ آيَةٌ مِنْ كِتَابِ اللَّهِ إِلاَّ أَنَا أَعْلَمُ فِيمَ أُنْزِلَتْ، وَلَوْ أَعْلَمُ أَحَدًا أَعْلَمَ مِنِّي بِكِتَابِ اللَّهِ تُبَلِّغُهُ الإِبِلُ لَرَكِبْتُ إِلَيْهِ.
“There is no Sura revealed in Allah's Book but I know at what place it was revealed”
Travelling for better knowledge
He said that if he knew of anyone who knew the Book of Allah better than he did, and could be reached by camel, he would go to him. Even with his status he stayed a student.
Try this today
However much you know, keep a teacher or a better-informed person in your sights.
Sit with this
Who knows more than you, and how could you reach them?
Source
Sahih al-Bukhari 5002Sahih قَالَ قَالَ عَبْدُ اللَّهِ ـ رضى الله عنه ـ وَاللَّهِ الَّذِي لاَ إِلَهَ غَيْرُهُ مَا أُنْزِلَتْ سُورَةٌ مِنْ كِتَابِ اللَّهِ إِلاَّ أَنَا أَعْلَمُ أَيْنَ أُنْزِلَتْ وَلاَ أُنْزِلَتْ آيَةٌ مِنْ كِتَابِ اللَّهِ إِلاَّ أَنَا أَعْلَمُ فِيمَ أُنْزِلَتْ، وَلَوْ أَعْلَمُ أَحَدًا أَعْلَمَ مِنِّي بِكِتَابِ اللَّهِ تُبَلِّغُهُ الإِبِلُ لَرَكِبْتُ إِلَيْهِ.
“if I know that there is somebody who knows Allah's Book better than I, and he is at a place that camels can reach, I would go to him”
Reciting it fresh, with care
The Prophet said that whoever wanted to recite the Quran as fresh as when it was revealed should recite it as Ibn Umm Abd does. This reflects a clear, measured, correct recitation, and he disliked rushing through it like poetry.
Try this today
Improve one aspect of your recitation, such as tajwid or pace, and practice it daily.
Sit with this
What one part of your recitation could you improve this month?
Sources
Sunan Ibn Majah 138Sahih أَنَّ أَبَا بَكْرٍ، وَعُمَرَ، بَشَّرَاهُ أَنَّ رَسُولَ اللَّهِ ـ صلى الله عليه وسلم ـ قَالَ " مَنْ أَحَبَّ أَنْ يَقْرَأَ الْقُرْآنَ غَضًّا كَمَا أُنْزِلَ فَلْيَقْرَأْهُ عَلَى قِرَاءَةِ ابْنِ أُمِّ عَبْدٍ".
“Whoever would like to recite the Qur'an as fresh as when it was revealed, let him recite it like Ibn Umm 'Abd”
Sahih al-Bukhari 775Sahih قَالَ سَمِعْتُ أَبَا وَائِلٍ، قَالَ جَاءَ رَجُلٌ إِلَى ابْنِ مَسْعُودٍ فَقَالَ قَرَأْتُ الْمُفَصَّلَ اللَّيْلَةَ فِي رَكْعَةٍ. فَقَالَ هَذًّا كَهَذِّ الشِّعْرِ لَقَدْ عَرَفْتُ النَّظَائِرَ الَّتِي كَانَ النَّبِيُّ صلى الله عليه وسلم يَقْرِنُ بَيْنَهُنَّ فَذَكَرَ عِشْرِينَ سُورَةً مِنَ الْمُفَصَّلِ سُورَتَيْنِ فِي كُلِّ رَكْعَةٍ.
“This recitation is (too quick) like the recitation of poetry”
One reminder a week, not more
He gave a talk to people every Thursday. When asked to do it daily, he said he did not want to bore them, and that he chose his times carefully just as the Prophet did with them.
Try this today
Share good reminders in small, well-timed doses so they are welcomed rather than tiring.
Sit with this
Are your reminders to others well timed, or too frequent to be welcome?
Source
Sahih al-Bukhari 70Sahih قَالَ كَانَ عَبْدُ اللَّهِ يُذَكِّرُ النَّاسَ فِي كُلِّ خَمِيسٍ، فَقَالَ لَهُ رَجُلٌ يَا أَبَا عَبْدِ الرَّحْمَنِ لَوَدِدْتُ أَنَّكَ ذَكَّرْتَنَا كُلَّ يَوْمٍ. قَالَ أَمَا إِنَّهُ يَمْنَعُنِي مِنْ ذَلِكَ أَنِّي أَكْرَهُ أَنْ أُمِلَّكُمْ، وَإِنِّي أَتَخَوَّلُكُمْ بِالْمَوْعِظَةِ كَمَا كَانَ النَّبِيُّ صلى الله عليه وسلم يَتَخَوَّلُنَا بِهَا، مَخَافَةَ السَّآمَةِ عَلَيْنَا.
“I hate to bore you”
Putting prayer on time and kindness to parents first
Asked which deed is dearest to Allah, the Prophet told him the prayer at its early time, then dutifulness to parents. He asked no more, knowing the Prophet would have answered more.
Try this today
Pray on time, and make a call or visit to a parent a regular part of your week.
Sit with this
Is your prayer on time, and when did you last call your parents?
Sources
Sahih al-Bukhari 527Sahih … الْعَيْزَارِ أَخْبَرَنِي قَالَ سَمِعْتُ أَبَا عَمْرٍو الشَّيْبَانِيَّ، يَقُولُ حَدَّثَنَا صَاحِبُ، هَذِهِ الدَّارِ وَأَشَارَ إِلَى دَارِ عَبْدِ اللَّهِ قَالَ سَأَلْتُ النَّبِيَّ صلى الله عليه وسلم أَىُّ الْعَمَلِ أَحَبُّ إِلَى اللَّهِ قَالَ" الصَّلاَةُ عَلَى وَقْتِهَا". قَالَ ثُمَّ أَىُّ قَالَ" ثُمَّ بِرُّ الْوَالِدَيْنِ". قَالَ ثُمَّ أَىُّ قَالَ" الْجِهَادُ فِي سَبِيلِ اللَّهِ". قَالَ …
“To offer the prayers at their early stated fixed times”
Sahih al-Bukhari 527Sahih … عَمْرٍو الشَّيْبَانِيَّ، يَقُولُ حَدَّثَنَا صَاحِبُ، هَذِهِ الدَّارِ وَأَشَارَ إِلَى دَارِ عَبْدِ اللَّهِ قَالَ سَأَلْتُ النَّبِيَّ صلى الله عليه وسلم أَىُّ الْعَمَلِ أَحَبُّ إِلَى اللَّهِ قَالَ" الصَّلاَةُ عَلَى وَقْتِهَا". قَالَ ثُمَّ أَىُّ قَالَ" ثُمَّ بِرُّ الْوَالِدَيْنِ". قَالَ ثُمَّ أَىُّ قَالَ" الْجِهَادُ فِي سَبِيلِ اللَّهِ". قَالَ حَدَّثَنِي بِهِنَّ وَلَوِ اسْتَزَدْتُهُ …
“To be good and dutiful to your parents”
Fearing one's sins and returning to Allah
He taught that a believer sees his sins like a mountain above him that might fall, while the wicked person sees them like a fly he brushes off, and he narrated the Prophet's words on how pleased Allah is with a person's repentance.
Try this today
Take small sins seriously and repent quickly, trusting Allah's pleasure in your return.
Sit with this
Do your small sins feel like a fly or like a mountain?
Source
Sahih al-Bukhari 6308Sahih … كَذُبَابٍ مَرَّ عَلَى أَنْفِهِ". فَقَالَ بِهِ هَكَذَا قَالَ أَبُو شِهَابٍ بِيَدِهِ فَوْقَ أَنْفِهِ. ثُمَّ قَالَ" لَلَّهُ أَفْرَحُ بِتَوْبَةِ عَبْدِهِ مِنْ رَجُلٍ نَزَلَ مَنْزِلاً، وَبِهِ مَهْلَكَةٌ، وَمَعَهُ رَاحِلَتُهُ عَلَيْهَا طَعَامُهُ وَشَرَابُهُ، فَوَضَعَ رَأْسَهُ فَنَامَ نَوْمَةً، فَاسْتَيْقَظَ وَقَدْ ذَهَبَتْ رَاحِلَتُهُ، حَتَّى اشْتَدَّ عَلَيْهِ الْحَرُّ وَالْعَطَشُ أَوْ مَا شَاءَ …
“A believer sees his sins as if he were sitting under a mountain”
Saying 'Allah knows best' when you do not know
He told the people that whoever knows something should say it, and whoever does not should say 'Allah knows best,' since that itself is a sign of knowledge.
Try this today
Admit what you do not know. It builds trust, and keeps you learning.
Sit with this
When did you last say "Allah knows best" instead of guessing?
Source
Sahih al-Bukhari 4809Sahih … قَالَ يَا أَيُّهَا النَّاسُ مَنْ عَلِمَ شَيْئًا فَلْيَقُلْ بِهِ، وَمَنْ لَمْ يَعْلَمْ فَلْيَقُلِ اللَّهُ أَعْلَمُ، فَإِنَّ مِنَ الْعِلْمِ أَنْ يَقُولَ لِمَا لاَ يَعْلَمُ اللَّهُ أَعْلَمُ، قَالَ اللَّهُ عَزَّ وَجَلَّ لِنَبِيِّهِ صلى الله عليه وسلم{قُلْ مَا أَسْأَلُكُمْ عَلَيْهِ مِنْ أَجْرٍ وَمَا أَنَا مِنَ الْمُتَكَلِّفِينَ} وَسَأُحَدِّثُكُمْ عَنِ الدُّخَانِ إِنَّ رَسُولَ اللَّهِ صلى …
“he should say, "Allah knows better,"”
Using knowledge for others
He narrated the Prophet's teaching that the two people to be envied are the one who spends wealth in the right way and the one who has been given wisdom, acts on it, and teaches it to others.
Try this today
Teach one thing you know, today, to someone who will benefit.
Sit with this
What one thing you know could you teach someone today?
Source
Sahih al-Bukhari 73Sahih … حَدَّثَنِي إِسْمَاعِيلُ بْنُ أَبِي خَالِدٍ، عَلَى غَيْرِ مَا حَدَّثَنَاهُ الزُّهْرِيُّ، قَالَ سَمِعْتُ قَيْسَ بْنَ أَبِي حَازِمٍ، قَالَ سَمِعْتُ عَبْدَ اللَّهِ بْنَ مَسْعُودٍ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم " لاَ حَسَدَ إِلاَّ فِي اثْنَتَيْنِ رَجُلٌ آتَاهُ اللَّهُ مَالاً فَسُلِّطَ عَلَى هَلَكَتِهِ فِي الْحَقِّ، وَرَجُلٌ آتَاهُ اللَّهُ الْحِكْمَةَ، فَهْوَ يَقْضِي بِهَا …
“he acts according to it and teaches it to others”
Virtues
The Prophet told the Companions to learn the recitation of the Quran from four people, and named Abdullah ibn Mas'ud first.
“Learn the recitation of the Qur'an from (any of these) four persons”
Arabic text
قَالَ ذُكِرَ عَبْدُ اللَّهِ عِنْدَ عَبْدِ اللَّهِ بْنِ عَمْرٍو، فَقَالَ ذَاكَ رَجُلٌ لاَ أَزَالُ أُحِبُّهُ بَعْدَ مَا سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ " اسْتَقْرِئُوا الْقُرْآنَ مِنْ أَرْبَعَةٍ مِنْ عَبْدِ اللَّهِ بْنِ مَسْعُودٍ، فَبَدَأَ بِهِ، وَسَالِمٍ مَوْلَى أَبِي حُذَيْفَةَ، وَأُبَىِّ بْنِ كَعْبٍ، وَمُعَاذِ بْنِ جَبَلٍ". قَالَ لاَ أَدْرِي بَدَأَ بِأُبَىٍّ أَوْ بِمُعَاذٍ.
Sahih al-Bukhari 3758Sahih
He said that he learned over seventy surahs directly from the Prophet, and that the Companions knew he was among those who knew the Book best.
“I learnt over seventy Suras direct from Allah's Messenger”
Arabic text
… بْنُ سَلَمَةَ، قَالَ خَطَبَنَا عَبْدُ اللَّهِ فَقَالَ وَاللَّهِ لَقَدْ أَخَذْتُ مِنْ فِي رَسُولِ اللَّهِ صلى الله عليه وسلم بِضْعًا وَسَبْعِينَ سُورَةً، وَاللَّهِ لَقَدْ عَلِمَ أَصْحَابُ النَّبِيِّ صلى الله عليه وسلم أَنِّي مِنْ أَعْلَمِهِمْ بِكِتَابِ اللَّهِ وَمَا أَنَا بِخَيْرِهِمْ. قَالَ شَقِيقٌ فَجَلَسْتُ فِي الْحِلَقِ أَسْمَعُ مَا يَقُولُونَ فَمَا سَمِعْتُ رَادًّا يَقُولُ غَيْرَ …
Sahih al-Bukhari 5000Sahih
He was close enough to the household of the Prophet that visitors from Yemen took him and his mother to be members of the family.
“we used to see him and his mother going in the house of the Prophet”
Arabic text
قَالَ سَمِعْتُ أَبَا مُوسَى الأَشْعَرِيَّ ـ رضى الله عنه ـ يَقُولُ قَدِمْتُ أَنَا وَأَخِي مِنَ الْيَمَنِ، فَمَكُثْنَا حِينًا مَا نُرَى إِلاَّ أَنَّ عَبْدَ اللَّهِ بْنَ مَسْعُودٍ رَجُلٌ مِنْ أَهْلِ بَيْتِ النَّبِيِّ صلى الله عليه وسلم، لِمَا نَرَى مِنْ دُخُولِهِ وَدُخُولِ أُمِّهِ عَلَى النَّبِيِّ صلى الله عليه وسلم.
Sahih al-Bukhari 3763Sahih
Sayings and moments
If someone knows something, let him say it; if he does not, let him say 'Allah knows best.'
“he should say, "Allah knows better,"”
Arabic text
… قَالَ يَا أَيُّهَا النَّاسُ مَنْ عَلِمَ شَيْئًا فَلْيَقُلْ بِهِ، وَمَنْ لَمْ يَعْلَمْ فَلْيَقُلِ اللَّهُ أَعْلَمُ، فَإِنَّ مِنَ الْعِلْمِ أَنْ يَقُولَ لِمَا لاَ يَعْلَمُ اللَّهُ أَعْلَمُ، قَالَ اللَّهُ عَزَّ وَجَلَّ لِنَبِيِّهِ صلى الله عليه وسلم{قُلْ مَا أَسْأَلُكُمْ عَلَيْهِ مِنْ أَجْرٍ وَمَا أَنَا مِنَ الْمُتَكَلِّفِينَ} وَسَأُحَدِّثُكُمْ عَنِ الدُّخَانِ إِنَّ رَسُولَ اللَّهِ صلى …
Sahih al-Bukhari 4809Sahih
There is no surah in the Book of Allah whose place of revelation I do not know.
“There is no Sura revealed in Allah's Book but I know at what place it was revealed”
Arabic text
قَالَ قَالَ عَبْدُ اللَّهِ ـ رضى الله عنه ـ وَاللَّهِ الَّذِي لاَ إِلَهَ غَيْرُهُ مَا أُنْزِلَتْ سُورَةٌ مِنْ كِتَابِ اللَّهِ إِلاَّ أَنَا أَعْلَمُ أَيْنَ أُنْزِلَتْ وَلاَ أُنْزِلَتْ آيَةٌ مِنْ كِتَابِ اللَّهِ إِلاَّ أَنَا أَعْلَمُ فِيمَ أُنْزِلَتْ، وَلَوْ أَعْلَمُ أَحَدًا أَعْلَمَ مِنِّي بِكِتَابِ اللَّهِ تُبَلِّغُهُ الإِبِلُ لَرَكِبْتُ إِلَيْهِ.
Sahih al-Bukhari 5002Sahih
Words on this page
- Badrبدر
- The first major battle between the Muslims and Quraysh, in 2 AH. Those who fought there hold a special rank among the Companions.
- Hadithحديث
- A report of what the Prophet ﷺ said, did or approved, passed down through a chain of narrators.
- Madinahالمدينة
- The city, formerly Yathrib, to which the Prophet ﷺ migrated and where the first Muslim community was built.
- Makkahمكة
- The city of the Ka'bah, where the Prophet ﷺ was born and revelation began.
- Qurayshقريش
- The leading tribe of Makkah, to which the Prophet ﷺ belonged, and which opposed him for most of his mission.
- Surahسورة
- A chapter of the Quran. There are 114.
- Ummahالأمة
- The worldwide community of Muslims.
- Wuduالوضوء
- The ritual washing of the face, arms, head and feet before prayer.
Related companions
- عبد الله بن عباسAbdullah ibn AbbasThe Prophet's young cousin for whom he prayed for understanding of the Book; the great early interpreter of t…
- زيد بن ثابتZayd ibn ThabitYoung Ansari scribe of the Prophet who wrote down revelation, later compiled the Quran under Abu Bakr and cop…
- خباب بن الأرتKhabbab ibn al-ArattOne of the earliest Muslims, a Meccan blacksmith who endured persecution for his faith and later worried abou…
- أبو بكر الصديقAbu Bakr al-SiddiqThe Prophet's closest companion and first caliph, remembered for truthfulness, tender-hearted worship and giv…
- عمر بن الخطابUmar ibn al-KhattabUmar ibn al-Khattab, al-Faruq and second caliph: his night prayer, justice, generosity and respect for the Bo…
Sources and review
- Wikipedia: Abd Allah ibn Mas'ud (opens in a new tab)
- Hadith texts and grades cross-checked against the fawazahmed0 hadith-api dataset (mirrors sunnah.com numbering) (opens in a new tab)
Hadith numbers follow sunnah.com. Each report links to sunnah.com, and, where the numbering matches, to al-Hadees or HadithUnlocked as well. Quran verses link to quran.com, Tafsir Ibn Kathir and Tanzil. The Arabic is taken from the hadith editions and trimmed around the quoted words, so read the full report at the source before relying on it. Grades are the ones those editions give.
This page is pending scholar review. It was compiled from public sources, and its citations were last checked on 7 October 2026. If you notice a mistake or a missing source, please tell us.