Narrated Zainab bint Um Salama:Um Sulaim said, "O Allah's Messenger (ﷺ)! Verily Allah is not shy of (telling you) the truth. Is it essential for a woman to take a bath after she had a wet dream (nocturnal sexual discharge)?" He said, "Yes, if she notices discharge. On that Um Salama laughed and said, "Does a woman get a (nocturnal sexual) discharge?" He said, "How then does (her) son resemble her (his mother)?"
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا يَحْيَى، عَنْ هِشَامٍ، قَالَ أَخْبَرَنِي أَبِي، عَنْ زَيْنَبَ بِنْتِ أُمِّ سَلَمَةَ، عَنْ أُمِّ سَلَمَةَ، أَنَّ أُمَّ سُلَيْمٍ، قَالَتْ يَا رَسُولَ اللَّهِ إِنَّ اللَّهَ لاَ يَسْتَحِي مِنَ الْحَقِّ، هَلْ عَلَى الْمَرْأَةِ غُسْلٌ إِذَا احْتَلَمَتْ قَالَ " نَعَمْ إِذَا رَأَتِ الْمَاءَ ". فَضَحِكَتْ أُمُّ سَلَمَةَ فَقَالَتْ أَتَحْتَلِمُ الْمَرْأَةُ فَقَالَ النَّبِيُّ صلى الله عليه وسلم " فَبِمَ شَبَهُ الْوَلَدِ ".
Bukhari
Good Manners and Form (Al-Adab) • Hadith 118