صحيح مسلم

'A'isha reported that Allah's Messenger (may peace he upon him) 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 Holy 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.