Sahih Muslim 2410 a
'A'isha reported that Allah's Messenger (may peace he upon him) lay on bed during one night and said:
Were there a pious person from amongst my companions who should keep a watch for me during the nightt? She said: We heard the noise of arms, whereupon Allah's Messenger (ﷺ) said: Who is it? And Sa'd b. Abi Waqqas said: Allah's MesseDger. I have come to serve as your sentinel. 'A'isha said: Allah' s Messenger (ﷺ) slept (such a sound sleep) that I heard the noise of his snoring.
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مَسْلَمَةَ بْنِ قَعْنَبٍ، حَدَّثَنَا سُلَيْمَانُ بْنُ بِلاَلٍ، عَنْ يَحْيَى بْنِ سَعِيدٍ،
 عَنْ عَبْدِ اللَّهِ بْنِ عَامِرِ بْنِ رَبِيعَةَ، عَنْ عَائِشَةَ، قَالَتْ أَرِقَ رَسُولُ اللَّهِ صلى الله عليه وسلم
 ذَاتَ لَيْلَةٍ فَقَالَ لَيْتَ رَجُلاً صَالِحًا مِنْ أَصْحَابِي يَحْرُسُنِي اللَّيْلَةَ ‏.‏ قَالَتْ وَسَمِعْنَا صَوْتَ السِّلاَحِ
 فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏
"‏ مَنْ هَذَا ‏"‏ ‏.‏ قَالَ سَعْدُ بْنُ أَبِي وَقَّاصٍ يَا رَسُولَ
 اللَّهِ جِئْتُ أَحْرُسُكَ ‏.‏ قَالَتْ عَائِشَةُ فَنَامَ رَسُولُ اللَّهِ صلى الله عليه وسلم حَتَّى سَمِعْتُ غَطِيطَهُ
 ‏.‏