Narrated 'Abdullah bin 'Amr: Once Allah's Messenger (saws) said to me, "I have been informed that you offer Salat (prayer) all the night and observe Saum (fast) during the day." I said, "(Yes) I do so." He said, "If you do so, your eye sight will become weak and you will become weak. No doubt, your body has right on you, and your family has right on you, so observe Saum (for some days) and do not observe it (for some days), offer Salat (for sometime) and then sleep."