It is narrated from al-Aswad that when Umar bin al-Khattab (may Allah be pleased with him) began the prayer, he would say the takbir, then say: 'Subhanaka Allahumma wa bihamdika, wa tabaraka ismuka, wa ta'ala jadduka, wa la ilaha ghayruk' (You are free of all imperfection, O Allah, and praise is Yours; Your name is blessed, Your majesty is exalted, and there is no true god besides You).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2350