Volume 8 · Book 78 · Hadith 691
Narrated 'Aisha: The Prophet said, "Whoever vowed to be obedient to Allah, must be obedient to Him; and whoever vowed to be disobedient to Allah, should not be disobedient to Him."
— Sahih Bukhari, Volume 8, Book 78: Oaths and Vows, Hadith #691