The Messenger of Allah ﷺ said, "The night prayer is performed two units at a time. You give the testimony of faith after every two units, show humility, display submissiveness, raise your hands in supplication, and say, 'Allah, forgive me.' Whoever does not do this, his prayer is deficient."
حدثنا أبو بكر بن أبي شيبة حدثنا شبابة بن سوار حدثنا شعبة حدثني عبد ربه بن سعيد عن أنس بن أبي أنس عن عبد الله بن نافع ابن العمياء عن عبد الله بن الحارث
قال رسول الله ﷺ صلاة الليل مثنى مثنى وتشهد في كل ركعتين وتباءس وتمسكن وتقنع وتقول اللهم اغفر لي فمن لم يفعل ذلك فهي خداج
Its chain of transmission is daif.Abu Dawud narrated it in the Book of Voluntary Prayers, chapter on daytime prayer, hadith no. 1296, from the hadith of Shubah with this wording. Ibn Khuzayma indicated its daif status, and Bukhari and Ibn Abdul-Barr and others also graded it daif. Ibn al-Amya was graded daif by the majority, and this grading of daif is the stronger view.