وَحَدَّثَنَا يَحْيَى بْنُ يَحْيَى التَّمِيمِيُّ، أَخْبَرَنَا أَبُو مُعَاوِيَةَ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنْ زَيْنَبَ بِنْتِ أَبِي سَلَمَةَ، عَنْ أُمِّ سَلَمَةَ، قَالَتْ جَاءَتْ أُمُّ سُلَيْمٍ إِلَى النَّبِيِّ صلى الله عليه وسلم فَقَالَتْ يَا رَسُولَ اللَّهِ إِنَّ اللَّهَ لاَ يَسْتَحْيِي مِنَ الْحَقِّ فَهَلْ عَلَى الْمَرْأَةِ مِنْ غُسْلٍ إِذَا احْتَلَمَتْ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ نَعَمْ إِذَا رَأَتِ الْمَاءَ ‏"‏ ‏.‏ فَقَالَتْ أُمُّ سَلَمَةَ يَا رَسُولَ اللَّهِ وَتَحْتَلِمُ الْمَرْأَةُ فَقَالَ ‏"‏ تَرِبَتْ يَدَاكِ فَبِمَ يُشْبِهُهَا وَلَدُهَا ‏"‏ ‏.‏

Umm Salama reported: Umm Sulaim went to the Messenger of Allah (PBUH) and said: Apostle of Allah, Allah is not ashamed of the truth. Is bathing necessary for a woman when she has a sexual dream? Upon this the Messenger of Allah (PBUH) said: Yes, when she sees the liquid (vaginal secretion). Umm Salama said: Messenger of Allah, does a woman have sexual dream? He (the Holy Prophet) said: Let your hand be covered with dust, in what way does her child resemble her? Translation Not Available

Book Ref: Sahih Muslim Book 3 Hadith 610
Web Ref:  Sahih Muslim Book 3 Hadith 313 a