Sahih Bukhari Volume 009, Book 093, Hadith Number 506.

Narrated By Abu Said Al-Khudri : That during the battle with Bani Al-Mustaliq they (Muslims) captured some females and intended to have sexual relation with them without impregnating them. So they asked the Prophet about coitus interrupt us. The Prophet said, "It is better that you should not do it, for Allah has written whom He is going to create till the Day of Resurrection." Qaza'a said, "I heard Abu Sa'id saying that the Prophet said, 'No soul is ordained to be created but Allah will create it."