Sahih Bukhari
Prophetic Commentary on the Quran (Tafseer of the Prophet (PBUH))
Volume: 006 / Book Number: 060 / Hadith Number: 138
Narrated Aisha:
That her father (Abu Bakr) never broke his oath till Allah revealed the order of the legal expiation for oath. Abu Bakr said, "If I ever take an oath (to do something) and later find that to do something else is better, then I accept Allah's permission and do that which is better, (and do the legal expiation for my oath ) ".