Musannaf Ibn Abi Shayba 1:982

Ibn Fudayl narrated to us, from al-A’mash, from Mujahid, who said: Regarding semen (al-maniyy), prostatic fluid (al-wady), and pre-seminal fluid (al-madhy): for semen, there is ghusl (full ritual washing). And for prostatic fluid and pre-seminal fluid, there is wudu (ablution).