The Messenger of Allah ﷺ used to say at the end of his witr prayer, "O Allah, I seek refuge in Your pleasure from Your displeasure, and in Your pardon from Your punishment, and I seek refuge in You from You. I cannot enumerate Your praise. You are as You have praised Yourself."
حدثنا موسى بن إسمعيل حدثنا حماد عن هشام بن عمرو الفزاري عن عبد الرحمن بن الحارث بن هشام
أن رسول الله ﷺ كان يقول في آخر وتره اللهم إني أعوذ برضاك من سخطك وبمعافاتك من عقوبتك وأعوذ بك منك لا أحصي ثناء عليك أنت كما أثنيت على نفسك
[Its isnad is sahih. Tirmidhi narrated it in the Book of Supplications, chapter on the supplication of Witr, hadith no. 3566, from the hadith of Hammad bin Salama, and he said, "Hasan gharib." Nasai also narrated it, hadith no. 1748, as did Ibn Majah, hadith no. 1179.]