Sahih al-Bukhari 97:25
Narrated Ibn `Abbas:
Allah's Messenger (ﷺ) said, "If anyone of you, when intending to have a sexual relation (sleep) with his wife, says: Bismillah, Allahumma jannibna ashShaitan, wa Jannib ash-Shaitana ma razaqtana, Satan would never harm that child, should it be ordained that they will have one. (Because of that sleep).
Reference
Sahih al-Bukhari 97:25
In-book reference
Book 97, Hadith 25
Arabic Text
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا جَرِيرٌ، عَنْ مَنْصُورٍ، عَنْ سَالِمٍ، عَنْ كُرَيْبٍ، عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " لَوْ أَنَّ أَحَدَكُمْ إِذَا أَرَادَ أَنْ يَأْتِيَ أَهْلَهُ فَقَالَ بِاسْمِ اللَّهِ، اللَّهُمَّ جَنِّبْنَا الشَّيْطَانَ، وَجَنِّبِ الشَّيْطَانَ مَا رَزَقْتَنَا. فَإِنَّهُ إِنْ يُقَدَّرْ بَيْنَهُمَا وَلَدٌ فِي ذَلِكَ لَمْ يَضُرُّهُ شَيْطَانٌ أَبَدًا ".