Al-Aswad narrates: Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) would recite "Qul huwa Allahu ahad" (Say: He is Allah, the One) in the last rak'ah of witr, then raise his hands and recite the qunut before bowing.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9393