Ibn Masʿūd and [the rest of] the Companions of the Prophet ﷺ used to say the qunūt supplication before bowing in the witr prayer.
Ibn Abī Shaybah, Al-Muṣannaf ḥadīth 6911, and others.
Al-Albānī states, commenting on the chain of transmission of the narration in Al-Maṣannaf:
This is a good (jayyid) chain of transmission, and it comforms to the conditions stipulated by Muslim (for his Ṣaḥīḥ) … in summary: that which is authentic and established from the Companions is qunūt before bowing in the witr prayer.
Irwāʾ Al-Ghalīl 2:166.