When the Prophet ﷺ opened the prayer, he would say, "Glory be to You, Allah, and praise be to You. Blessed is Your name, exalted is Your majesty, and there is no god but You."
حدثنا علي بن محمد وعبد الله بن عمران قالا حدثنا أبو معاوية حدثنا حارثة بن أبي الرجال عن عمرة
أن النبي ﷺ كان إذا افتتح الصلاة قال سبحانك اللهم وبحمدك تبارك اسمك وتعالى جدك ولا إله غيرك
[Hasan]. Reported by Tirmidhi, in Salah, the chapter on what is said when opening the prayer, hadith no. 243, from the hadith of Abu Muawiya, and see hadith no. 56 for its defect, and hadith no. 804 as a corroborating witness for it.