Book “Qada Amiralmuminin Ali ibn AbuTalib”, author Muhammad Taqi Tustari, at page 37, he said:

Translation:

First: Kulayni narrated from Sadiq (alaihi salam): A man brought his wife to Umar, and said: This woman of mine is black, and I am black, and she bore white child. Umar said to those who were present – What is your view on this? They said – We think that she should be stoned, because she is black, her husband is black and she bore white. Amiralmuminin came when she was taken to stoning, and he said to the black (man) – D0 you accuse her? He said – No. Imam said – You entered upon her when she had her menstruation? He answered – In the night from the nights she said me that he is menstruating, and I thought that she refuse intercourse due to coldness of weather, and come to her.  Imam said to woman – He entered upon you while you was menstruating? She said yes, his weapon (allegory) was taken upon him, and (I) couldn’t say (answer).  Imam said: GO BACK, HE IS YOUR SON, BLOOD (OF MENSTRUATION) OVERPOWERED SPERM, SO IT COULD BE BLACK (DUE TO THIS). WHEN HE WOULD GROW HE WOULD BECOME BLACK (1).

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1) Correct that he would become black, as it is in “Jamiul Madarik” (4/455), and not white as it is in text of  Tustari’s book.