Musannaf Ibn Abi Shayba 1:1486

Ibn ‘Ulayyah narrated to us, from Ibn Abi ‘Arubah and others, from al-Hasan, regarding a man who performs ghusl (ritual bath) for janabah (major ritual impurity), then something of semen exits from his penis: He said: If he had urinated before he performed ghusl, then he does not repeat the ghusl. And if he had not urinated, then he should repeat the ghusl.