سنن ابن ماجه

It was narrated from Ibn 'Abbas that: He came to Ubayy bin Ka'b accompanied by 'Umar. Ubayy came out to them and said: "I noticed some prostatic fluid, so I washed my penis and performed ablution. 'Umar said: "Is that sufficient?" He said: "Yes." He ('Umar) asked: "Did you hear that from the messenger of Allah?" He said: "Yes."