All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.
Allaah, The Exalted, has assigned guardian angels to protect and watch over each and every human being; He says (what means): {For each one are successive (angels) before and behind him who protect him by the decree of Allaah...} [Quran 13:11]
Ibn Katheer wrote, “They are four angels at night and four angels during the day. Two angels, on the right and the left, record his deeds. The one on the right writes down his good deeds and the one on the left writes down his evil deeds. Two other angels guard him and protect him, one from behind and one from the front. So, there are four angels by day and four others by night.” [Tafseer Ibn Katheer]
Allaah, The Exalted, also says (what means): {And indeed, (appointed) over you are keepers, noble and recording. They know whatever you do.} [Quran 82:10-12]
Ibn Jurayj wrote, "They are two angels; one on the right of every slave to record the good deeds and the other on the left to record the bad deeds. They come to people in succession by night and day." It was narrated on the authority of Abu Hurayrah that the Prophet, sallallaahu ʻalayhi wa sallam, said, “Angels come to you in succession by night and day, and they all gather at the time of the Fajr and ʻAsr prayers. Those who passed the night with you ascend (to Heaven), and Allaah asks them, though He knows best, 'In what state did you leave My slaves?' The angels reply, 'When we left them, they were praying, and when we reached them, they were praying.'" [Al-Bukhari and Muslim]
Ibn Zamaneen narrated in his book As-Sunnah that Al-Hasan said, "The guardian angels who take turns in guarding each slave are four; two by night and two by day. They gather together at the time of the Fajr Prayer."
Each human being has a constant companion (Qareen) from the angels as well. ʻAbdullaah ibn Masʻood narrated that the Prophet, sallallaahu ʻalayhi wa sallam, said, "There is none amongst you but to whom there is assigned a constant companion from among the jinn and a constant companion from among the angels." [Muslim]
Mullaa ʻAli Al-Qaari commented on the hadeeth, "The hadeeth refers to the angel appointed as a constant companion (Qareen) for each human being to inspire him with goodness and virtue, and that angel is known as 'Al-Mulhim' (meaning the one who inspires)..."
Abu Ash-Shaykh cited in his book Al-ʻAthamah on the authority of ʻAbdullaah ibn Al-Mubaarak that he said, "There are five angels appointed to accompany each person; two angels accompany him during the day and another two accompany him during the night, and there is a fifth angel that constantly accompanies him all day and night and does not leave him..."
Allaah knows best.