‘Abdullah b. ‘Amr (Allah be pleased with both of them) reported: The Messenger of Allah (may peace be upon him) said to me: I have been informed that you stand for prayer the whole of night and fast during the day. I said: I do that, whereupon he said: If you did that you in fact strained heavily your eyes and made yourself weak. There is a right of your eyes (upon you) and a right of yourself (upon you) and a right of your family (upon you). Stand for prayer and sleep, observe fasts and break (them).
Chapter : Forbiddance to observe perpetual fast and excellence of observing fast on alternate days.