‏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)....

‏الحيض : Hadeeth No:597 'A'isha reported: Whenever the Messenger of Allaah (sallAllaahu alayhi wa sallam) intended to sleep after having sexual intercourse, he performed ablution as for the prayer before going to sleep....