Anas reported that the Messenger of Allah ﷺ observed Qunut for one month invoking curse upon some tribes of Arabia (those who were responsible for the murders in Bi'r Ma'una and Raji'), but then abandoned it. (Using translation from Muslim 677j)  

أَنَّ رَسُولَ اللهِ ﷺ قَنَتَ شَهْرًا يَدْعُو عَلَى حَيٍّ مِنْ أَحْيَاءِ الْعَرَبِ ثُمَّ تَرَكَهُ  

"I prayed behind the Messenger of Allah ﷺ 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." (Using translation from Nasāʾī 1080)  

صَلَّيْتُ خَلْفَ النَّبِيِّ ﷺ 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 بُنَيَّ إِنَّهَا بِدْعَةٌ