The scribe of Sayyiduna al-Mughirah bin Shu'bah (may Allah be pleased with him) relates that Mu'awiyah (may Allah be pleased with him) wrote to al-Mughirah bin Shu'bah (may Allah be pleased with him): Did the Messenger of Allah (peace and blessings be upon him) use to say anything after the prayer? He said: He (peace and blessings be upon him) would say: "There is no true god except Allah, He is alone, He has no partner; His is the dominion and to Him belongs all praise, and He has power over all things. O Allah, none can withhold what You give, and none can give what You withhold, and the greatness of one who has greatness avails him nothing against You."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 18062