It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "If a person, when approaching his wife for intimacy, recites this supplication: «اَللّٰهُمَّجَنِّبْنِيالشَّيْطَانَوَجَنِّبْالشَّيْطَانَمَارَزَقْتَنِي» 'In the name of Allah, O Allah! Protect me from Satan and protect what You grant us (of offspring) from Satan,' then if it is decreed that they have a child from that encounter, Satan will never be able to harm that child."
Hadith Referenceمسند احمد / ومن مسند بني هاشم / 2597