Hadith 1445

Ibn 'Abbas (May Allah be pleased with them) reported: The Prophet (PBUH) said, "If anyone intends to have (sexual intercourse) with his wife, he should say: "Bismillah! Allahumma janibnash-Shaitana, wa jannibish-Shaitana ma razaqtana (In the Name of Allah, O Allah! Keep us away from Satan and keep Satan away from what You have bestowed upon us);' and if Allah has ordained a child for them, Satan will never harm him."

[Al-Bukhari and Muslim].