Sahih Bukhari Volume 008, Book 078, Hadith Number 665.
Narated By Ubai bin Ka'b : That he heard Allah's Apostle 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."
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 , "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.)