It is narrated from Sayyiduna Zayd bin Arqam (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) used to recite this supplication after the prayer: "O Allah, You are our Lord and the Lord of everything; I bear witness that Muhammad (peace and blessings be upon him) is Your servant and Messenger. O Allah, You are our Lord and the Lord of everything; I bear witness that all the servants are brothers to one another. O Allah, You are our Lord and the Lord of everything; make me and my family sincere to You in this world and the Hereafter. O Possessor of Majesty and Honour, hear and answer. Allah is the Greatest, the Greatest. O Allah, You are the Light of the heavens and the earth. Allah is the Greatest, the Greatest. Allah is sufficient for me, and He is the best Disposer of affairs. Allah is the Greatest, the Greatest."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 5103