Hadith 6114
`A'isha said: When God's messenger arrived in Medina, he was wakeful one night and said, "Would that a good man would guard me!" We then heard the sound of weapons, and when he asked who was there Sa'd replied that it was he. He asked what had brought him and he replied, "Fear for God's messenger occurred to me, so I came to guard him. Invoking a blessing on him, God's messenger then went to sleep. (Bukhari and Muslim.)
وَعَن عَائِشَة قَالَتْ: سَهِرَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ مَقْدِمَهُ الْمَدِينَةَ لَيْلَةً فَقَالَ: «لَيْتَ رَجُلًا صَالِحًا يَحْرُسُنِي» إِذْ سَمِعْنَا صَوْتَ سِلَاحٍ فَقَالَ: «مَنْ هَذَا؟» قَالَ: أَنَا سَعْدٌ قَالَ: «مَا جَاءَ بِكَ؟» قَالَ: وَقَعَ فِي نَفْسِي خَوْفٌ عَلَى رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَجِئْتُ أَحْرُسُهُ فَدَعَا لَهُ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ثُمَّ نَامَ. مُتَّفَقٌ عَلَيْهِ