Yahya related to me from Malik from Nafi that Abdullah ibn Umarused to do kaffara for a broken oath by feeding ten poor people. Eachperson got a mudd of wheat. He sometimes freed a slave if he hadrepeated the oath. (IT)
USC-MSA web (English) reference: Book 22, Hadith 13 (IT)
Arabic reference (IT): Book 22, Hadith 1025 (IT)