Sahih Bukhari
Funerals (Al-Janaaiz)
Volume: 002 / Book Number: 023 / Hadith Number: 467
Narrated Abu Huraira:
The Prophet said, "Every child is born with a true faith of Islam (i.e. to worship none but Allah Alone) and his parents convert him to Judaism or Christianity or Magianism, as an animal delivers a perfect baby animal. Do you find it mutilated?"