كتاب الفضائل
9
The Book of Virtues
Abu Hurairah (May Allah be pleased with him) reported:
The Messenger of Allah (ﷺ) said, "There are angels who take turns in visiting you by night and by day, and they all assemble at the dawn (Fajr) and the afternoon ('Asr) prayers. Those who have spent the night with you, ascend to the heaven and their Rubb, Who knows better about them, asks: 'In what condition did you leave My slaves?' They reply: 'We left them while they were performing Salat and we went to them while they were performing Salat."'

[Al-Bukhari and Muslim].

وعن أبي هريرة رضي الله عنه قال‏:‏ قال رسول الله صلى الله عليه وسلم‏:‏ ‏ "‏يتعاقبون فيكم ملائكة بالليل، وملائكة بالنهار، ويجتمعون في صلاة الصبح وصلاة العصر، ثم يعرج الذين باتوا فيكم، فيسألهم الله -وهو أعلم بهم-‏:‏ كيف تركتم عبادي‏؟‏ فيقولون تركناهم وهم يصلون، وأتيناهم وهم يصلون‏"‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏‏.‏
Sunnah.com reference : Book 9, Hadith 60
Arabic/English book reference : Book 9, Hadith 1050