The Prophet ﷺ said, "If anyone of you, when having sexual intercourse with his wife, says: Bismillah, Allahumma jannibni-Sh-Shaitan wa jannib-ish-Shaitan ma razaqtana, and if it is destined that they should have a child, then Satan will never be able to harm him."  

قَالَ النَّبِيُّ ﷺ أَمَا لَوْ أَنَّ أَحَدَهُمْ يَقُولُ حِينَ يَأْتِي أَهْلَهُ بِاسْمِ اللَّهِ اللَّهُمَّ جَنِّبْنِي الشَّيْطَانَ وَجَنِّبِ الشَّيْطَانَ مَا رَزَقْتَنَا ثُمَّ قُدِّرَ بَيْنَهُمَا فِي ذَلِكَ أَوْ قُضِيَ وَلَدٌ لَمْ يَضُرَّهُ شَيْطَانٌ أَبَدًا