Sahih Muslim Book - 5, Hadith - 1549

وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِى شَيْبَةَ وَأَبُو كُرَيْبٍ قَالاَ حَدَّثَنَا أَبُو مُعَاوِيَةَ عَنْ عَاصِمٍ عَنْ أَنَسٍ قَالَ سَأَلْتُهُ عَنِ الْقُنُوتِ قَبْلَ الرُّكُوعِ أَوْ بَعْدَ الرُّكُوعِ فَقَالَ قَبْلَ الرُّكُوعِ. قَالَ قُلْتُ فَإِنَّ نَاسًا يَزْعُمُونَ أَنَّ رَسُولَ اللَّهِ -صلى الله عليه وسلم- قَنَتَ بَعْدَ الرُّكُوعِ. فَقَالَ إِنَّمَا قَنَتَ رَسُولُ اللَّهِ -صلى الله عليه وسلم- شَهْرًا يَدْعُو عَلَى أُنَاسٍ قَتَلُوا أُنَاسًا مِنْ أَصْحَابِهِ يُقَالُ لَهُمُ الْقُرَّاءُ.

It was narrated from "Asim from Anas; he said: "I asked him about Qunut, is it before bowing or after bowing?" He (Anas) said: "Before bowing." I said: "Some people are saying that the Messenger of Allah (s.a.w) said the Qunut after bowing." He said: "The Messenger of Allah (s.a.w) said the Qunut for a month, supplicating against people who had killed some of his Companions, who were known as Al-Qurra' (the reciters)."