It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that once the Prophet (peace and blessings be upon him) said: "The night prayer consists of two rak'ahs at a time. When you fear that dawn is approaching, then add one rak'ah to these two." Someone asked Sayyiduna Ibn Umar (may Allah be pleased with them both), "What does 'two at a time' mean?" He replied: "It means that you should say salam after every two rak'ahs."