Mishkat al-Masabih 1292
Abu Malik al-Ashja‘i said:
I said to my father, “Father, you have prayed behind God’s Messenger, Abu Bakr, ‘Umar and ‘Uthman, and behind Ali here in al-Kufa for about five years. Did they stand in humble supplication?” He replied, “Sonny, it is an innovation.” 

Tirmidhi, Nasa’i and Ibn Majah transmitted it.
وَعَن أبي مَالك الْأَشْجَعِيّ قَالَ: قُلْتُ لِأَبِي: يَا أَبَتِ إِنَّكَ قَدْ صليت خَلْفَ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَأَبِي بكر وَعمر وَعُثْمَان وَعلي هَهُنَا بِالْكُوفَةِ نَحْوًا مِنْ خَمْسِ سِنِينَ أَكَانُوا يَقْنُتُونَ؟ قَالَ: أَيْ بُنَيَّ مُحْدَثٌ ". رَوَاهُ التِّرْمِذِيُّ وَالنَّسَائِيُّ وَابْن مَاجَه