Muwatta Malik 1022

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّهُ كَانَ يُكَفِّرُ عَنْ يَمِينِهِ، بِإِطْعَامِ عَشَرَةِ مَسَاكِينَ لِكُلِّ مِسْكِينٍ مُدٌّ مِنْ حِنْطَةٍ وَكَانَ يَعْتِقُ الْمِرَارَ إِذَا وَكَّدَ الْيَمِينَ ‏.‏

Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to do kaffara for a broken oath by feeding ten poor people. Each person got a mudd of wheat. He sometimes freed a slave if he had repeated the oath

Reference

Muwatta Malik 1022

In-book

Book 22, Hadith 9