Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) narrates: The Noble Prophet (peace and blessings be upon him) used to recite "Surah Al-A'la," "Surah Al-Kafirun," and "Surah Al-Ikhlas" in the three rak'ahs of Witr, and he would recite the Qunoot supplication before going into bowing (ruku'). Then, when he finished with salam, he would say "Subhana al-Malik al-Quddus," and in the last time he would raise his voice, and he would say: "Rabb al-mala'ikati wa al-ruh," meaning "Lord of the angels and the spirit."
Hadith Referenceسنن الدارقطني / كتاب الوتر / 1660
Hadith Takhrij«أخرجه ابن الجارود فى ((المنتقى)) 299، وابن حبان فى ((صحيحه)) برقم: 2436، 2450، والحاكم فى ((مستدركه)) برقم: 3034، والنسائي فى ((المجتبیٰ)) برقم: 1698 ، وأبو داود فى ((سننه)) برقم: 1423، 1430، وابن ماجه فى ((سننه)) برقم: 1171، 1182، والدارقطني فى ((سننه)) برقم: 1659، 1660، 1661، والطبراني فى ((الأوسط)) برقم: 1666، 8115» «: (4 / 330)»