It is narrated from Sayyiduna Wathilah bin al-Asqa' (may Allah be pleased with him) that when the Messenger of Allah (peace and blessings be upon him) began the prayer, he would recite this supplication: 'Subhanaka Allahumma wa bihamdika, wa tabaraka ismuka, wa ta'ala jadduka, wa la ilaha ghayruka' (O Allah, You are free of all imperfection and to You belongs all praise; blessed is Your name, exalted is Your majesty, and there is no god besides You).
Hadith Referenceالمعجم الكبير للطبراني / باب الواو / 18375