Mukhtasar Muslim

It is narrated from Sayyiduna Ibn 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 Prophet (peace and blessings be upon him) said: The night prayer is (offered) two by two rak‘ahs. Then when you fear that dawn is approaching, pray one rak‘ah, for it will make what you have prayed an odd number.