Muwatta Imam Malik Book of Vows and Oaths, Hadith 12

Yahya related to me from Malik from Nafi that Abdullah ibn Umar said, "If someone breaks an oath which he has stressed, he has to free a slave, or clothe ten poor people. If someone breaks an oath, but has not stressed it, he only has to feed ten poor people and each poor person is fed a mudd of wheat. Some one who does not have the means for that, should fast for three days."

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّهُ كَانَ يَقُولُ مَنْ حَلَفَ بِيَمِينٍ فَوَكَّدَهَا ثُمَّ حَنِثَ فَعَلَيْهِ عِتْقُ رَقَبَةٍ أَوْ كِسْوَةُ عَشَرَةِ مَسَاكِينَ وَمَنْ حَلَفَ بِيَمِينٍ فَلَمْ يُؤَكِّدْهَا ثُمَّ حَنِثَ فَعَلَيْهِ إِطْعَامُ عَشَرَةِ مَسَاكِينَ لِكُلِّ مِسْكِينٍ مُدٌّ مِنْ حِنْطَةٍ فَمَنْ لَمْ يَجِدْ فَصِيَامُ ثَلاَثَةِ أَيَّامٍ .