Musannaf Ibn Abi Shayba 1:976

Ibn ‘Ulayyah narrated to us, from Ibn ‘Awn, from Muhammad, who said: They mentioned to Ibn ‘Umar the *balah* (pre-seminal fluid) and the *madhy* (prostatic fluid), and some of what a man finds. He said: "You are mentioning something that I do not find, and if I were to find it, I would perform *ghusl* (full ritual washing) because of it."