Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: "The night prayer is two (rak'ahs) by two, and (after every two rak'ahs) there is a salam."
Imam al-Tabarani (may Allah have mercy on him) said: "Only Ali bin Salih narrated this hadith from Mughirah, and only Salamah al-Awsi from Ali, and Yahya bin Uthman is alone in narrating it."