'A'isha reported that Allah's Messenger (ﷺ) laid down on bed during one night on his arrival at Medina and said:

Were there a pious person from amongst my Companions who should keep a watch for me durin. the night? She (A'isha) reported: We were in this state that we heard the clanging noise of arms. lie (the Prophet) said: Who is it? He said: This is Sa'd b. Abi Waqqas. Allah's Messenger (ﷺ) said to him: What brings you here? Thereupon he said: I harboured fear (lest any harm should come to) Allah's Messenger (ﷺ), so I came to serve as your sentinel. Allah's Messenger (ﷺ) invoked blessings upon him. He then slept. This hadith has been transmitted on the authority of Ibn Rumh with a slight variation of wording.

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا لَيْثٌ، ح وَحَدَّثَنَا مُحَمَّدُ بْنُ رُمْحٍ، أَخْبَرَنَا اللَّيْثُ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنْ عَبْدِ اللَّهِ بْنِ عَامِرِ بْنِ رَبِيعَةَ، أَنَّ عَائِشَةَ، قَالَتْ سَهِرَ رَسُولُ اللَّهِ صلى الله عليه وسلم مَقْدَمَهُ الْمَدِينَةَ لَيْلَةً فَقَالَ ‏"‏ لَيْتَ رَجُلاً صَالِحًا مِنْ أَصْحَابِي يَحْرُسُنِي اللَّيْلَةَ ‏"‏ ‏.‏ قَالَتْ فَبَيْنَا نَحْنُ كَذَلِكَ سَمِعْنَا خَشْخَشَةَ سِلاَحٍ فَقَالَ ‏"‏ مَنْ هَذَا ‏"‏ ‏.‏ قَالَ سَعْدُ بْنُ أَبِي وَقَّاصٍ ‏.‏ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ مَا جَاءَ بِكَ ‏"‏ ‏.‏ قَالَ وَقَعَ فِي نَفْسِي خَوْفٌ عَلَى رَسُولِ اللَّهِ صلى الله عليه وسلم فَجِئْتُ أَحْرُسُهُ ‏.‏ فَدَعَا لَهُ رَسُولُ اللَّهِ صلى الله عليه وسلم ثُمَّ نَامَ ‏.‏ وَفِي رِوَايَةِ ابْنِ رُمْحٍ فَقُلْنَا مَنْ هَذَا