Sahih Bukhari

Narrated By 'Uqba bin 'Amir Al-Juhani : That the Prophet distributed among his companions some animals for sacrifice (to be slaughtered on 'Id-al-Adha). 'Uqba's share was a Jadha'a (a six month old goat). 'Uqba said, "O Allah's Apostle! I get in my share of Jadha'a (a six month old ram)." The Prophet said, "Slaughter it as a sacrifice."