حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مَسْلَمَةَ بْنِ قَعْنَبٍ، حَدَّثَنَا حَمَّادُ بْنُ سَلَمَةَ، عَنْ ثَابِتٍ الْبُنَانِيِّ، عَنْ أَنَسٍ، أَنَّ النَّبِيَّ صلى الله عليه وسلم كَانَ مَعَ إِحْدَى نِسَائِهِ فَمَرَّ بِهِ رَجُلٌ فَدَعَاهُ فَجَاءَ فَقَالَ ‏"‏ يَا فُلاَنُ هَذِهِ زَوْجَتِي فُلاَنَةُ ‏"‏ ‏.‏ فَقَالَ يَا رَسُولَ اللَّهِ مَنْ كُنْتُ أَظُنُّ بِهِ فَلَمْ أَكُنْ أَظُنُّ بِكَ ‏.‏ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ إِنَّ الشَّيْطَانَ يَجْرِي مِنَ الإِنْسَانِ مَجْرَى الدَّمِ ‏"‏ ‏.‏

Anas reported that when Allah's Messenger (PBUH) 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: 0 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 (PBUH) said: Verily Satan circulates in the body like blood. Translation Not Available

Book reference: Sahih Muslim Book 39 Hadith 5404
Web reference: Sahih Muslim Book 26 Hadith 2174