It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "The Maghrib prayer is the witr of the day, so you should also perform the witr of the night. The night prayer is offered in sets of two rak‘ahs, and the witr is one rak‘ah in the last part of the night."