‏الأيمان : Hadeeth No:4053 Abu Huraira reported Allaah's Messenger (sallAllaahu alayhi wa sallam) as saying: He who took an oath and then found another thing better than (this) should expiate for the oath (broken) by him and do (the better thing)....

‏الزكاة : Hadeeth No:2175 Abu Dharr reported: I went out one night (and found) the Messenger of Allaah (sallAllaahu alayhi wa sallam) walking all alone. There was no man with him. I thought that he did not like anyone walking along with him. So I began to walk in the light of the moon. He, however turned his attention to me ...