Sunan an-Nasa'i, Volume 2, Book 12, Hadith 1081 (DarusSalam) ⓘ

It was narrated from Abu Malik Al-Ashja'i that his father said: "I prayed behind the Messenger of Allah and he did not say the Qunut, and I prayed behind Abu Bakr and he did not say the Qunut, and I prayed behind Umar and he did not say the Qunut, and I prayed behind Uthman and he did not say the Qunut, and I prayed behind Ali and he did not say the Qunut." Then he said: "O my son, this is an innovation."

أَخْبَرَنَا قُتَيْبَةُ، عَنْ خَلَفٍ، - وَهُوَ ابْنُ خَلِيفَةَ - عَنْ أَبِي مَالِكٍ الأَشْجَعِيِّ، عَنْ أَبِيهِ، قَالَ صَلَّيْتُ خَلْفَ رَسُولِ اللَّهِ صلى الله عليه وسلم فَلَمْ يَقْنُتْ وَصَلَّيْتُ خَلْفَ أَبِي بَكْرٍ فَلَمْ يَقْنُتْ وَصَلَّيْتُ خَلْفَ عُمَرَ فَلَمْ يَقْنُتْ وَصَلَّيْتُ خَلْفَ عُثْمَانَ فَلَمْ يَقْنُتْ وَصَلَّيْتُ خَلْفَ عَلِيٍّ فَلَمْ يَقْنُتْ ثُمَّ قَالَ يَا بُنَىَّ إِنَّهَا بِدْعَةٌ ‏.‏