Harun bin Ishaq bin Muhammad هارون بن إسحاق بن محمد بن مالك · The Book on Salat (Prayer)

Allah's Messenger said: "When one of you is sleepy and he is performing Salat, then let him lie down until the sleep is gone from him. For when one of you performs Salat while he is sleepy, perhaps he wants to seek forgiveness but he curses himself."