From Sahih Muslim (Hadith 695):
Ali reported:I was one whose prostatic fluid flowed readily and I was ashamed to ask the Apostle (ﷺ) about it, because of the position of his daughter. I, therefore, asked Miqdad. b. al-Asad and he inquired of him (the Holy Prophet). He (the Holy Prophet) said: He should wash his male organ and perform ablution
Reference: Muslim 695