I say, and with God's success: It is necessary to perform ghusl (ritual washing) upon seeing madhi (pre-seminal fluid), even if one does not remember having a wet dream; due to the possibility that it is semen that has become thin due to the body's heat, and the discharge of semen necessitates ghusl. Aisha (may Allah be pleased with her) said: "The Messenger of Allah (peace be upon him) was asked about a man who finds wetness but does not remember having a wet dream. He said: He should perform ghusl. And about a man who thinks he has had a wet dream but does not find wetness, he said: There is no ghusl upon him." Umm Salama said: "O Messenger of Allah, is there ghusl upon a woman who sees that?" He said: "Yes, women are the counterparts of men." This is found in Sunan al-Tirmidhi 1: 190, Sunan al-Sughra 1: 112, Al-Muntaka 1: 33, Sunan Abu Dawood 1: 78, and Musnad Ahmad 6: 256. Refer to: Tabyeen al-Haqa'iq 1: 16, and Allah knows best.