that he heard Allah's Messenger (ﷺ) saying, "(Moses) said, 'Call me not to account for what I forget and be not hard upon me for my affair (with you)' (18.73) the first excuse of Moses was his forgetfulness."
Sahih al-Bukhari Book 83, Hadith 50
← Previous Hadith that Allah's Prophet led them in the Zuhr prayer and he offered either more or less rak`at, and it was said to him, "O Allah's Messenger (ﷺ) ! Has the prayer been reduced, or have you forgotten?" He asked, "What is that?" They said, "You have prayed so many rak`at." So he performed with them two more prostrations and said, "These two prostrations are to be performed by the person who does not know whether he has prayed more or less (rak`at) in which case he should seek to follow what is right. And then complete the rest (of the prayer) and perform two extra prostrations."

Sahih al-Bukhari Book 83, Hadith 49 Next Hadith → Narrated Al-Bara bin Azib that once he had a guest, so he told his family (on the Day of Id-ul-Adha) that they should slaughter the animal for sacrifice before he returned from the ('Id) prayer in order that their guest could take his meal. So his family slaughtered (the animal ) before the prayer. Then they mentioned that event to the Prophet who ordered Al-Bara to slaughter another sacrifice. Al-Bara' said to the Prophet (ﷺ) , "I have a young milch she-goat which is better than two sheep for slaughtering." (The sub-narrator, Ibn 'Aun used to say, "I don't know whether the permission (to slaughter a she-goat as a sacrifice) was especially given to Al-Bara' or if it was in general for all the Muslims.") (See Hadith No. 99, Vol. 2.)

Sahih al-Bukhari Book 83, Hadith 51