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."
Muwatta Malik Book 22, Hadith 13