Authentic Supplication Number 241.

It is reported that the Prophet  said:" Were it that when one of you come to his wife he should say:Bismillahi, 'allahumma jannibna 'ash-shaytana, wajannib 'ash-shaytana ma razaqtana (251), then if a son were decreed between them, no shaytan would ever harm him".

Footnotes.
(251) In The Name of Allah, O' my 'ilah avoid us the shaytan, and avoid the shaytan that which you You have granted us.

Reporters.
Agreed upon by Bukhari and Muslim. Al-Albani included this hadeeth in The Authentic of Good Sayings as #166.