Musannaf Ibn Abi Shayba 3:5628

Hushaym narrated to us, from Mughirah, from Ibrahim, who said: He used to say, "Indeed, the devil runs in the urethra and pulses at the anus, so the man thinks that he has broken wind. Therefore, let none of you depart until he hears a sound, or finds a smell, or sees wetness."