بُلُوغُ الْمَرَامِ
Bulugh al-Maram 306
The Book of Prayer
وَعَنْهُ أَنَّ اَلنَّبِيَّ - صلى الله عليه وسلم -{ كَانَ لَا يَقْنُتُ إِلَّا إِذَا دَعَا لِقَوْمٍ , أَوْ دَعَا عَلَى قَوْمٍ } صَحَّحَهُ اِبْنُ خُزَيْمَةَ . [1]
Narrated [Anas (RA)]: The Prophet (ﷺ) never used to supplicate [i.e. Qunut in the prayer) except when he prayed for a people or when he prayed against a people. [Ibn Khuzaimah graded it Sahih (authentic)].
Sunnah.com reference: Book 2, Hadith 192