Allah, exalted be His praise, says: "Then its expiation is feeding ten poor persons from the average of what you feed your families" [Surah al-Ma'idah: 89].
Imam al-Shafi'i (may Allah have mercy on him) said: "In the expiation for an oath, one mudd (per poor person) by the mudd of the Prophet (peace and blessings be upon him) suffices, because a 'araq (basket) of dates was brought to the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) gave it to a man and ordered him to feed sixty poor persons with it. The 'araq is estimated at fifteen sa', which makes sixty mudd, one mudd for each poor person."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / Q19968
Sayyiduna Abu Hurayrah (may Allah be pleased with him) said: A man came to the Prophet (peace and blessings be upon him) and said: O Messenger of Allah (peace and blessings be upon him)! I am ruined. He (peace and blessings be upon him) said: "Woe to you! What happened?" He said: In Ramadan I had intercourse with my wife. He (peace and blessings be upon him) said: "Free a slave." He said: I do not have one. He (peace and blessings be upon him) said: "Fast two consecutive months." He said: I am not able. He (peace and blessings be upon him) said: "Feed sixty poor persons." He said: I cannot. Then a basket of dates containing fifteen sa' was brought to the Prophet (peace and blessings be upon him). He (peace and blessings be upon him) said: "Take it and give it in charity." He said: To people poorer than my family? And he said: There is no one between these two mountains more needy than my family. The Prophet (peace and blessings be upon him) smiled until his molar teeth became visible. The Prophet (peace and blessings be upon him) said: "Take it, seek Allah's forgiveness, and feed it to your family."
Abu al-Hasan al-Daraqutni said: This chain is sahih (authentic).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19968
Sa'id bin al-Musayyib (may Allah have mercy on him) said: A Bedouin came to the Messenger of Allah (peace and blessings be upon him), and he mentioned (the story of) the one who had gone to his wife in the month of Ramadan. Ata (may Allah have mercy on him) said: I asked Sa'id (may Allah have mercy on him): How much was in the basket? He said: Between fifteen and twenty sa'.
The hadith of Ibn al-Musayyib is munqati' (its chain is broken), and others are more reliable than Ata al-Khurasani.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19969
In another narration from Ibn al-Musayyib (may Allah have mercy on him), fifteen sa' are mentioned without doubt. Sayyiduna Abu Hurayrah (may Allah be pleased with him) said: We were with the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) mentioned the man who had had intercourse with his wife. In it is: "Feed sixty poor persons." He said: "I cannot." A basket of dates containing fifteen sa' was brought to him (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Take it and feed sixty poor persons."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19970
Sa'id bin al-Musayyib (may Allah have mercy on him) said: A man came to the Messenger of Allah (peace and blessings be upon him) and mentioned that he had had intercourse with his wife. In it is that a basket of dates containing fifteen sa' was brought to the Prophet (peace and blessings be upon him), for sixty poor persons, and he (peace and blessings be upon him) said: "Take it and give it in charity."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19971
Nafi' narrates from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that he used to give the expiation for an oath by feeding ten poor persons, one mudd of wheat for each person, and sometimes he would also free a slave when the oath was emphatic.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19973
Ikrimah (may Allah have mercy on him) narrates from Ibn Abbas (may Allah be pleased with them both) that for each poor person there was one mudd of wheat, while a quarter of it was for curry (to eat with it).
(b) Ata (may Allah have mercy on him) narrates from Ibn Abbas (may Allah be pleased with them both) that for each poor person there was one mudd each.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19974
Ata said: I heard Abu Hurayrah (may Allah be pleased with him) in this mosque saying: There are three things in which there is one mudd each: 1. the expiation for an oath, 2. the expiation for zihar, 3. the fidyah of feeding a poor person.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19975
Sulayman bin Yasar (may Allah have mercy on him) said: I found the people giving the smaller mudd of wheat in the expiation for an oath, and they held that this suffices.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19976
Al-Hasan (may Allah have mercy on him) and Sa'id bin al-Musayyib (may Allah have mercy on him) held that in the expiation for an oath, one mudd of wheat or one mudd of barley suffices.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19977
Yasar bin Numayr said that Sayyiduna Umar (may Allah be pleased with him) said: I swear that I will not give certain people anything, but later I give to them. When you see that I have done this, then on my behalf feed ten poor persons, giving every two poor persons one sa' of wheat or one sa' of dates.
This was the view of Sayyiduna Umar (may Allah be pleased with him). Perhaps he considered more to be recommended, or perhaps less than this also suffices.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19978