Sahih Muslim | Book 26 | Hadith Number 5404
Narrated by Anas
Anas reported that when Allah's Messenger (may peace be upon him) was in the company of one of his wives a person happened to pass by them. He called him and when he came, he said to him: O so and so, she was my such and such wife. Thereupon he said, Allah's Messenger, if I were to doubt at all, I would have entertained no doubt about you at least. Thereupon Allah's Messenger (may peace be upon him) said: Verily Satan circulates in the body like blood.