Sahih Ibn Khuzaymah

Abdah bin Abi Lubabah narrates from Hazrat Zar bin Hubaysh or Suwaid bin Ghaflah the hadith of Sayyiduna Abu Darda or Sayyiduna Abu Dharr (may Allah be pleased with them) that they said: Whoever regularly prays at any part of the night, then misses it due to sleep, Allah Almighty writes the reward of that prayer for him, and his sleep will be a charity from Allah Almighty upon him. “Hazrat Abdah (may Allah have mercy on him) has explained the reason for the chain of this hadith in which he is doubtful whether he heard this hadith from Zar or from Suwaid? He has stated that both these teachers were together at one place, so one of them narrated this hadith, then he became doubtful about the narrator and the listener (as to who it was).”