Muwatta Imam Malik (Riwayat Ibn al-Qasim)

It is narrated from Sayyiduna Miqdad bin Aswad (may Allah be pleased with him) that Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) instructed him to ask the Messenger of Allah (peace and blessings be upon him) about a man who, when he goes to his wife, experiences the emission of madhi (pre-seminal fluid); what is obligatory upon such a man? Sayyiduna Ali (may Allah be pleased with him) said: Because the daughter of the Messenger of Allah (peace and blessings be upon him) is my wife, I feel shy to ask the Messenger of Allah (peace and blessings be upon him) about this issue. Miqdad (may Allah be pleased with him) said: So I asked the Messenger of Allah (peace and blessings be upon him) about it, and he said: "If any of you experiences such a condition, he should wash his private part with water and perform wudu for prayer."