The devil circulates in the son of Adam like blood. I feared lest he should cast evil thoughts in your hearts
Authentic hadithعن صَفِيَّةُ بِنْتُ حُيَيٍّ رضي الله عنها قالت: «كان النبي صلى الله عليه وسلم مُعْتَكِفًا، فَأَتَيْتُهُ أَزُورُهُ ليلا، فَحَدَّثْتُهُ، ثمَّ قُمْتُ لِأَنْقَلِبَ، فقام معي لِيَقْلِبَنِي -وكان مسكنها في دار أُسَامَةَ بن زَيْدٍ-، فَمَرَّ رَجُلاَنِ من الأنصار، فلما رأيا رسول الله صلى الله عليه وسلم أسرعا، فقال النبي صلى الله عليه وسلم : على رِسْلِكُمَا، إنها صَفِيَّةَ بِنْتُ حُيَيٍّ، فقالا: سبحان الله يا رسول الله، فقال: إن الشَّيْطَانَ يَجْرِي من ابن آدم مَجْرَى الدَّمِ، وإني خَشِيتُ أن يَقْذِفَ في قُلُوبِكُمَا شرا -أو قال شيئا-». وفي رواية: «أنها جاءَت تَزُورُهُ في اعْتِكَافِهِ في الْمَسْجِدِ، فِي العَشْرِ الأوَاخِرِ من رمضان، فتَحدَّثَتْ عنده ساعة، ثم قامت تَنقَلِبُ، فقام النبي صلى الله عليه وسلم معها يَقْلِبُهَا ، حتى إذا بَلَغَتْ باب المسجد عند باب أم سلمة...» ثم ذكره بمعناه.
Safiyyah bint Huyai (may Allah be pleased with her) reported: The Prophet (may Allah's peace and blessings be upon him) was once observing I‘tikāf, so I went to visit him at night. We talked for a while then I got up to leave. He got up with me to escort me - her dwelling was in the house of Usāmah ibn Zayd. Two men from the Ansār passed by. When they saw the Messenger of Allah (may Allah's peace and blessings be upon him) they quickened their pace, so he said to them: "Slow down. This is Safiyyah bint Huyai (my wife)." They said: "Subhān Allah! O Messenger of Allah," meaning: You are far above any suspicion. He said: "The devil circulates in the son of Adam like blood. I feared lest he should cast evil thoughts in your hearts (or he said: would cast something in your hearts)." Another narration reads: "Safiyyah came to visit him while he was observing I‘tikāf in the mosque during the last ten nights of Ramadan. So she stayed to talk to him for some time then got up to leave. The Prophet (may Allah's peace and blessings be upon him) got up to escort her until she reached the door of the mosque near Umm Salāmah's door..." Then the rest of the narration was reported with the same meaning.
Explanation
The Prophet (may Allah's peace and blessings be upon him) was observing I‘tikāf during the last ten nights of Ramadan. His wife, Safiyyah (may Allah be pleased with her) visited him one of those nights and talked to him for some time. Then she got up to go back home, so the Prophet got up with her to escort her and keep her company. Two men from the Ansār walked by, and when they saw the Prophet (may Allah's peace and blessings be upon him) they sped up out of shyness when they saw his wife with him. So the Prophet (may Allah's peace and blessings be upon him) said to them: Slow down for this is only my wife Safiyyah. The two men said in embarrassment: Subhān Allah! Is it even conceivable that someone might have suspicions about you (i.e. suspecting that the woman with him was not his wife)? In reply, the Prophet (may Allah's peace and blessings be upon him) informed them that the devil is keen on luring the sons of Adam, and that he is highly capable of doing so, for he runs through their veins just like blood given the subtle ways he sneaks into their hearts and minds. Therefore, he feared that the devil might cast suspicions in their hearts.
Source · Narrated by Bukhari & Muslim
From the Hadith Encyclopedia (hadeethenc.com).