Mishkat al-Masabih 433, 434

Umm Salama told how Umm Sulaim said, “Messenger of God, God is not ashamed of the truth. Is any washing necessary for a woman when she has a sexual dream?” He replied, “Yes, when she sees signs of liquid.” Umm Salama then covered her face and said, “Messenger of God, does a woman have sexual dreams?” He replied, “Of course she does. In what way does her child resemble her?”
(Bukhari and Muslim.) Muslim added in the version of Umm Sulaim, “The man’s liquid is coarse and white, the woman’s fine and yellow, so the resemblance comes from the one which prevails or comes first.”