“The Messenger of Allah (ﷺ) said: ‘The night prayers are (to be offered) two by two. Say the Tashah-hud after each two Rak`ah, and raise your hands in all humility like one who is poor and needy and say: ‘Allāhummaghfir lī (O Allah, forgive me).’ And whoever does not do that, it is imperfect.’”
Sunan Ibn Majah Book 5, Hadith 523