Narrated Ubayy ibn Ka'b:

Al-Hasan reported: Umar ibn al-Khattab gathered the people (in tarawih prayer) behind Ubayy ibn Ka'b (who led them). He used to lead them for twenty days (during Ramadan, and would not recite the supplication except in the second half of it (i.e. Ramadan). When the last ten days remained, he kept away from them, and prayed in his house. They used to say: Ubayy ran away. Abu Dawud said: This tradition shows that whatever has been reported about the recitation of the supplication is not tenable. Moreover, these two traditions from Ubayy b. Ka'b indicate that another tradition which tells that the Prophet (ﷺ) recited the supplication in the witr is weak.

حَدَّثَنَا شُجَاعُ بْنُ مَخْلَدٍ، حَدَّثَنَا هُشَيْمٌ، أَخْبَرَنَا يُونُسُ بْنُ عُبَيْدٍ، عَنِ الْحَسَنِ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، جَمَعَ النَّاسَ عَلَى أُبَىِّ بْنِ كَعْبٍ فَكَانَ يُصَلِّي لَهُمْ عِشْرِينَ لَيْلَةً وَلاَ يَقْنُتُ بِهِمْ إِلاَّ فِي النِّصْفِ الْبَاقِي فَإِذَا كَانَتِ الْعَشْرُ الأَوَاخِرُ تَخَلَّفَ فَصَلَّى فِي بَيْتِهِ فَكَانُوا يَقُولُونَ أَبَقَ أُبَىٌّ ‏.‏ قَالَ أَبُو دَاوُدَ وَهَذَا يَدُلُّ عَلَى أَنَّ الَّذِي ذُكِرَ فِي الْقُنُوتِ لَيْسَ بِشَىْءٍ وَهَذَانِ الْحَدِيثَانِ يَدُلاَّنِ عَلَى ضَعْفِ حَدِيثِ أُبَىٍّ أَنَّ النَّبِيَّ صلى الله عليه وسلم قَنَتَ فِي الْوِتْرِ ‏.‏