Mukhtasar Bukhari

Narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Some angels come to you in succession during the night and some during the day, and they all gather at the Fajr and Asr prayers. Then those angels who have stayed with you during the night ascend (to the heavens), and their Lord asks them, although He knows best about His servants, 'In what condition did you leave My servants?' They say, 'We left them while they were praying, and when we arrived to them (then also) they were praying.'"