Sahih Muslim
The Book of Faith (Kitab Al-Iman)
Book Number: 001 / Hadith Number: 204
In the hadith narrated by Shu'ba the words are: Verily the Messenger of Allah (may peace be upon him) said: He who took an oath on a religion other than Islam as a liar would become so as he said, and he who slaughtered himself with a thing would be slaughtered with that on the Day of Resurrection.