The Hadith (Inspired Sayings) of Muhammed
Angels keep records of prayer attendance -- Sahih Buhari-- Volume 4, Book 54, Number 433:
Narrated Abu Huraira: The Prophet said, "On every Friday the angels take heir stand at every gate of the mosques to write the names of the people chronologically (i.e. according to the time of their arrival for the Friday prayer and when the Imam sits (on the pulpit) they fold up their scrolls and get ready to listen to the sermon."
Narrated Abu Huraira: Allah's Apostle said, "When the Imam, during the prayer, says, "Allah hears him who praises Him', say: 'O Allah! Our Lord! All the praises are for You/, for if the saying of anyone of you coincides with the saying of the angels, his past sins will be forgiven."
Narrated Abu Huraira: The Prophet said, "As long as any-one of you is waiting for the prayer, he is considered to be praying actually, and the angels say, 'O Allah! Be merciful to him and forgive him', (and go on saying so) unless he leaves his place of praying or passes wind (i.e. breaks his ablution)."
Narrated Abu Said Al-Khudri: The Prophet said, "If while you are praying, somebody intends to pass in front of you, prevent him; and should he insist, prevent him again; and if he insists again, fight with him (i.e. prevent him violently e.g. pushing him violently), because such a person is (like) a devil."