It wasnarrated that Muttalib that is, Ibn Abu Wada'ah said:
"TheMessenger of Allah (ﷺ) said: 'The night prayers are (to beoffered)two by two. Say the Tashah-hud after each two Rak`ah, andraise yourhands in all humility like one who is poor and needy andsay:'Allāhummaghfir lī (O Allah, forgive me).' And whoever doesnot dothat, it is imperfect.'" (ES)
English reference (ES): Vol. 1, Book 5, Hadith 1325 (ES)
Arabic reference (ES): Book 5, Hadith 1386 (ES)