[Machine] A Jewish man passed by the Messenger of Allah ﷺ while he was talking to his Companions. The Quraish said to him, "O Jew, he claims to be a prophet. Ask him about something that only a prophet would know." So, he came and sat down and said, "O Muhammad, from what is man created?" He replied, "O Jew, man is created from both the sperm of the man and the sperm of the woman. As for the sperm of the man, it is thick and from it bones and nerves are formed. And as for the sperm of the woman, it is thin and from it flesh and blood are formed." Then the Jewish man stood up and left. Abu Abdullah Ata ibn As-Sa'ib said, "He had changed."  

مَرَّ يَهُودِيٌّ بِرَسُولِ اللهِ ﷺ وَهُوَ يُحَدِّثُ أَصْحَابَهُ قَالَ قَالَتْ قُرَيْشٌ يَا يَهُودِيُّ إِنَّ هَذَا يَزْعُمُ أَنَّهُ نَبِيٌّ فَقَالَ لَأَسْأَلَنَّهُ عَنْ شَيْءٍ لَا يَعْلَمُهُ إِلَّا نَبِيٌّ فَجَاءَ حَتَّى جَلَسَ فَقَالَ يَا مُحَمَّدُ مِمَّ يُخْلُقُ الْإِنْسَانُ؟ قَالَ يَا يَهُودِيُّ مِنْ كُلٍّ يُخْلَقُ مِنْ نُطْفَةِ الرَّجُلِ وَمِنْ نُطْفَةِ الْمَرْأَةِ فَأَمَّا نُطْفَةُ الرَّجُلِ فَنُطْفَةٌ غَلِيظَةٌ فَمِنْهَا الْعَظْمُ وَالْعَصَبُ وَأَمَّا نُطْفَةُ الْمَرْأَةِ فَنُطْفَةٌ رُقَيْقَةٌ فَمِنْهَا اللَّحْمُ وَالدَّمُ فَقَامَ الْيَهُودِيُّ وَاللَّفْظُ لِأَحْمَدَ قَالَ أَبُو عَبْدِ الرَّحْمَنِ عَطَاءُ بْنُ السَّائِبِ كَانَ قَدْ تَغَيَّرَ  

In case a woman sees that, she must take a bath. Umm Sulaim said: I was bashful on account of that and said: Does it happen? Upon this the Messenger of Allah ﷺ said: Yes (it does happen), otherwise how can (a child) resemble her? Man's discharge (i. e. sperm) is thick and white and the discharge of woman is thin and yellow; so the resemblance comes from the one whose genes prevail or dominate. (Using translation from Muslim 311)   

أَنَّ أُمَّ سُلَيْمٍ سَأَلَتِ النَّبِيَّ ﷺ عَنِ الْمَرْأَةِ تَرَى فِي مَنَامِهَا مَا يَرَى الرَّجُلُ فَقَالَ النَّبِيُّ ﷺ «إِذَا رَأَتِ الْمَاءَ فَلْتَغْتَسِلْ» قَالَتْ أُمُّ سَلَمَةَ وَاسْتَحْيَيْتُ مِنْ ذَلِكَ وَهَلْ يَكُونُ ذَلِكَ يَا رَسُولَ اللهِ؟ قَالَ «نَعَمْ إِنَّ مَاءَ الرَّجُلِ غَلِيظٌ أَبْيَضُ وَمَاءُ الْمَرْأَةِ رَقِيقٌ أَصْفَرُ فَمِنْ أَيِّهِمَا عَلَا أَوْ سَبَقَ كَانَ مِنْهُ الشَّبَهُ»  

Umm Sulaim asked the Messenger of Allah about a woman who sees in her dream something like that which a man sees. The Messenger of Allah said: "If she sees that and has a discharge, then let her perform a bath." Umm Salamah said: "O Messenger of Allah, does that really happen?" He said: "Yes, the water of the man is thick and white and the water of a woman is thin and yellow. Whichever of them comes first or predominates, the child will resemble (that parent)." (Using translation from Ibn Mājah 601)   

أَنَّهَا سَأَلَتْ رَسُولَ اللهِ ﷺ عَنِ الْمَرْأَةِ تَرَى فِي مَنَامِهَا مَا يَرَى الرَّجُلُ فَقَالَ رَسُولُ اللهِ ﷺ «إِذَا رَأَتِ الْمَرْأَةُ ذَلِكَ أَوْ إِحْدَاكُنَّ فَلْتَغْتَسِلْ» قَالَتْ أُمُّ سَلَمَةَ أَوَ يَكُونُ هَذَا؟ قَالَ رَسُولُ اللهِ ﷺ «مَاءُ الْمَرْأَةِ رَقِيقٌ أَصْفَرُ وَمَاءُ الرَّجُلِ غَلِيظٌ أَبْيَضُ فَمِنْ أَيُّهُمَا سَبَقَ أَوْ عَلَا يَكُونُ الشَّبَهُ»