Ablutions (Wudu')
Ṣaḥīḥ al-Bukhārī 141
بِسْمِ اللَّهِ اللَّهُمَّ جَنِّبْنَا الشَّيْطَانَ وَجَنِّبِ الشَّيْطَانَ مَا رَزَقْتَنَا. فَقُضِيَ بَيْنَهُمَا وَلَدٌ، لَمْ يَضُرَّهُ
bismi-Llāh Allāhumma jannibnā ash-shayṭāna wajannibi ash-shayṭāna mā razaqtanā. faquḍiya baynahumā waladun, lam yaḍurrah
Transliteration generated from the Arabic vowel marks
The full narration
Narrated Ibn `Abbas:The Prophet (ﷺ) said, "If anyone of you on having sexual relations with his wife said (and he must say it before starting) 'In the name of Allah. O Allah! Protect us from Satan and also protect what you bestow upon us (i.e. the coming offspring) from Satan,' and if it is destined that they should have a child then, Satan will never be able to harm that offspring
Source
Ṣaḥīḥ al-Bukhārī · 141
Ṣaḥīḥ
- Agreed upon as authentic (al-Bukhārī / Muslim)