Answered by Shaykh Faraz Rabbani
There is a discussion saying Witr is not a must and therefore one is not supposed to pray Witr as it is not mentioned in the Quran.
وَلَوْ رَدُّوهُ إِلَى الرَّسُولِ وَإِلَى أُولِي الأمْرِ مِنْهُمْ لَعَلِمَهُ الَّذِينَ يَسْتَنْبِطُونَهُ مِنْهُمْ
وَلَوْلا فَضْلُ اللَّهِ عَلَيْكُمْ وَرَحْمَتُهُ لاتَّبَعْتُمُ الشَّيْطَانَ إِلا قَلِيلا
Allah tells us in the Qur’an,
“If they had only referred it to the Messenger, or to those of authority among them, those capable of legal inference would have known it. Were it not for the Grace and Mercy of Allah unto you, all but a few of you would have fallen into the clutches of Satan.” [4.83]
The ruling of witr is that it is wajib (necessary), and thus sinful to leave. [Haskafi, al-Durr al-Mukhtar]
This is because of many hadiths of the Beloved Messenger of Allah (Allah bless him and give him peace) in which he most emphatically emphasized the witr prayer. [Ibn al-Humam, Fath al-Qadir]
Among these hadiths: The Prophet (Allah bless him and give him peace) said,
“Witr is a duty, so whoever does not perform witr is not of us,” and he repeated it three times. [Abu Dawud and Ahmad; the hadith is sound, as discussed by Zayla`i in Nasb al-Raya (2.112) and`Ayni in `Umdat al-Qari Sharh Sahih al-Bukhari (7.11);]
And Allah alone gives success.
Wassalam,
Faraz Rabbani