Musannaf Ibn Abi Shayba 1:969

969. Muhammad ibn Bishr narrated to us, he said: Mis'ar narrated to us, from Mus'ab ibn Shaybah, from Abu Habib ibn Ya'la ibn Munabbih, from Ibn Abbas, that he came to Ubayy, and Umar was with him. He (Ubayy) came out to them and said: "I found (some) madhy (prostatic fluid), so I washed my penis and performed wudu." Umar said: "Does that suffice?" He said: "Yes." He said: "Did you hear it from the Prophet, may Allah bless him and grant him peace?" He said: "Yes."