Beginning of Creation
Bukhari :: Book 4 :: Volume 54 :: Hadith 493
Narrated Ibn 'Abbas:
The Prophet said, "If anyone of you, when having sexual relation with his wife, say: 'In the name of Allah. O Allah! Protect us from Satan and prevent Satan from approaching our offspring you are going to give us,' and if he begets a child (as a result of that relation) Satan will not harm it."