It was narrated from Ibn ‘Abdur-Rahman bin Abza from his father that the Messenger of Allah صلی اللہ علیہ وآلہ وسلم used to recite in Witr: “Glorify the Name of your Lord, the Most High;” and: “Say: you disbelievers!;” and: “Say: He is Allah, (the) One.” And after he had said the Salam, he would say:
‘Subi (Glory be to the Sovereign, the Most Holy)’ three times, raising his voice with it the third time. (Sahih)