Sahih Muslim Book 8, Hadith Number 3361.

Chapter: What is to be supplicated at the time of sexual intercourse?

Ibn “Abbas (Allah be pleased with them) reported that Allah’s Messenger (May peace be upon him) said: If anyone amongst you intends to go to his wife he should say: In the name of Allah, O Allah protect us against Satan and keep away the Satan from the one that you have bestowed upon us, and if He has ordained a male child for them, Satan will never be able to do any harm to him.