عَنْ عُرْوَةَ بْنِ الزُّبَيْرِ عَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا أَنَّ امْرَأَةً قَالَتْ لِلنَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ: هَلْ تَغْتَسِلُ الْمَرْأَةُ إِذَا احْتَلَمَتْ وَأَبْصَرَتِ الْمَاءَ؟ فَقَالَ: ((نَعَمْ)) فَقَالَتْ لَهَا عَائِشَةُ: تَرِبَتْ يَدَاكِ، فَقَالَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ: ((دَعِيهَا، وَهَلْ يَكُونُ الشَّبَهُ إِلَّا مِنْ قِبَلِ ذَلِكَ، إِذَا عَلَا مَاؤُهَا مَاءَ الرَّجُلِ أَشْبَهَ أَخَوَالَهُ، وَإِذَا عَلَا مَاءُ الرَّجُلِ مَاءَهَا أَشْبَهَهُ))
Lady Aisha (may Allah be pleased with her) narrates that a woman asked the Holy Prophet (peace and blessings be upon him): If a woman experiences a wet dream and sees fluid, should she perform ghusl (ritual bath)? The Prophet (peace and blessings be upon him) replied: Yes. Lady Aisha (may Allah be pleased with her) said to that woman: May your hands be dusted, but the Prophet (peace and blessings be upon him) said to her: Leave this woman (she is right). It is for this reason that resemblance occurs: when the woman’s fluid prevails over the man’s fluid, the child resembles the maternal uncles, and when the man’s fluid prevails over the woman’s fluid, the child’s resemblance is to him.