Abu Bakr never used to break an oath until Allah revealed the expiation for oaths. Then he said, "I will not swear an oath and later see something better than it without doing what is better and offering expiation for my oath."
أن أبا بكر رضي الله عنه لم يكن يحنث في يمين قط، حتى أنزل الله كفارة اليمين، وقال: لا أحلف على يمين، فرأيت غيرها خيرا منها، إلا أتيت الذي هو خير وكفرت عن يميني.
Bukhari narrated it in the Book of Oaths and Vows (6621), from Muhammad bin Muqatil Abu Hasan, who said, Abdullah (Ibn Mubarak) informed us, Hisham bin Urwa informed us, from his father, from Ayesha, and he related it as mentioned.Muhammad bin Abdul-Rahman Tufawi contradicted him, narrating it from Hisham bin Urwa, from his father, from Ayesha, who said, "The Messenger of Allah ﷺ, whenever he swore an oath, would not break it, until Allah the Exalted revealed the expiation for oaths. Then he said, 'I do not swear an oath and then see something better than it without expiating my oath, and then doing what is better.'"This Muhammad bin Abdul-Rahman Tufawi is disputed, though his hadith is hasan when he does not contradict others. Ibn Main deemed him trustworthy, and Abu Dawud said, "There is no harm in him." However, Abu Zura said, "His hadith is munkar (rejected)." And Ibn Adi said, "Most of his narrations are singular and unusual reports, but they are all acceptable, and his hadith is recorded."I say, this is one of the reports he narrated uniquely, and the incident actually happened to Abu Bakr, not to the Prophet ﷺ.