It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that a man asked the Messenger of Allah (peace and blessings be upon him) about the night prayer. The Messenger of Allah (peace and blessings be upon him) said: "The night prayer is in sets of two rak'ahs. Then when one of you fears that morning is approaching, he should pray one rak'ah, and that will make what he has prayed an odd number (witr) for him."