بُلُوغُ الْمَرَامِ
Bulugh al-Maram 304
The Book of Prayer
وَعَنْ أَنَسِ بْنِ مَالِكٍ - رضى الله عنه - { أَنَّ رَسُولَ اَللَّهِ - صلى الله عليه وسلم -قَنَتَ شَهْرًا بَعْدَ اَلرُّكُوعِ , يَدْعُو عَلَى أَحْيَاءٍ مِنْ أَحْيَاءِ اَلْعَرَبِ , ثُمَّ تَرَكَهُ } مُتَّفَقٌ عَلَيْهِ . [1]
Narrated Anas bin Malik (RA): The Prophet (ﷺ) recited Qunut (supplication in the prayer) for one month after (rising up from the) bowing (position), invoking curse on some Arab tribes. Afterwards, he gave it up. [Agreed upon].
Sunnah.com reference: Book 2, Hadith 190