Sahih Bukhari
Hunting, Slaughtering
Volume: 007 / Book Number: 067 / Hadith Number: 415
Narrated 'Aisha:
A group of people said to the Prophet, "Some people bring us meat and we do not know whether they have mentioned Allah's Name or not on slaughtering the animal." He said, "Mention Allah's Name on it and eat." Those people had embraced Islam recently.