While bowing in prayer

Glory to my Lord the Exalted (three times in Arabic)

Reference:Abu Dawud, Ibn Majah, An-Nasa'i, At-Tirmidhi, and Ahmad. See Al-Albani's Sahih At-Tirmidhi 1/83.Hisnul Muslim 33

سُبْـحانَ رَبِّـيَ الْعَظـيم (ثلاث مرات)

Transliteration

Subḥāna Rabbiyal-`Aẓīm.

Translation

Glory to my Lord the Exalted (three times in Arabic)