Riyad us Saliheen: Hadith 1421

The Messenger of Allah (ﷺ) took hold of my hand and said, "O Mu'adh! By Allah I love you, so I advise you to never forget to recite after every prayer: "Allahumma a'inni ala dhikrika, wa shukrika, wa husni 'ibadatika (O Allah, help me remember You, to be grateful to You, and to worship You in an excellent manner)."

[Abu Dawud].