كتاب الْمَسَاجِدِ وَمَوَاضِعِ الصَّلاَةِ
5  
The Book of Mosques and Places of Prayer
(54)
Chapter: It is recommended to say qunut in all prayers if a calamity befalls the Muslims – and refuge is sought from Allah (regarding that). It is recommended to say qunut in Subh at all times. And the clarification that it is to be said after raising the head from bowing in the final rak`ah, and it is recommended to say it out loud
(54)
باب اسْتِحْبَابِ الْقُنُوتِ فِي جَمِيعِ الصَّلاَةِ إِذَا نزَلَتْ بِالْمُسْلِمِينَ نَازِلَةٌ ‏‏
Sahih Muslim 677 d

Anas b. Malik reported that the Messenger of Allah (ﷺ) observed Qunut for a month in the dawn prayer after ruku' and invoked curse upon Bani Usayya.

وَحَدَّثَنِي مُحَمَّدُ بْنُ حَاتِمٍ، حَدَّثَنَا بَهْزُ بْنُ أَسَدٍ، حَدَّثَنَا حَمَّادُ بْنُ سَلَمَةَ، أَخْبَرَنَا أَنَسُ بْنُ سِيرِينَ، عَنْ أَنَسِ بْنِ مَالِكٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَنَتَ شَهْرًا بَعْدَ الرُّكُوعِ فِي صَلاَةِ الْفَجْرِ يَدْعُو عَلَى بَنِي عُصَيَّةَ ‏.‏
Reference : Sahih Muslim 677d
In-book reference : Book 5, Hadith 381
USC-MSA web (English) reference : Book 4, Hadith 1436
  (deprecated numbering scheme)