Ubayy bin Kaab reported,

When the Messenger of Allah ﷺ sat at the end of his Witr prayer, he would say, meaning after the salutation, "Glory be to the King, the Most Holy," three times.

Azami 11072

Sahih

عن أبي بن كعب قال

كان رسول الله ﷺ إذا جلس في آخر صلاته في الوتر يقول: يعني بعد التسليم: سبحان الملك القدوس ثلاثا.

الأعظمي 11072صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Supplications, remembrances, and prayer upon the chosen Prophet ﷺ
Chapter
Supplications of adhan and prayer, and what is related to them
Section
What is said after the salam of Witr
Numbering
Jami al-Kamil 11072 (2nd edition)
Azami 11072