It is narrated on the authority of Auf Ibn Malik Ashja'i (RA) that the Prophet (ﷺ) used to say in ruku:

سُبْحَانَ ذِي الْجَبَرُوْتِ وَالْمَلَكُوْتِ وَالْكِبْرِيَاءِ وَالْعَظَمَةِ

Subhaana dhil-jabarooti, wal-malakooti, wal-kibriyaa'i, wal-'adhamah

Glory is to You, Master of power, of dominion, of majesty and greatness. Then he prostrated and paused as long as he stood and recited Surat Aal Imran and then recited other surahs one after another.

Reference: Sahih (Albani). Abu Dawud: 873