Oaths and Vows (Kitab Al-Aiman Wa Al-Nudhur)
Dawud :: Book 21 : Hadith 3285
Narrated Aisha, Ummul Mu'minin:
The Prophet (peace_be_upon_him) as saying: No vow must be taken to do an act of disobedience, and the atonement for it is the same as for an oath.