The Messenger of Allah ﷺ said, "When one of you bows, let him say in his bowing, 'Glory be to my Lord, the Magnificent,' three times. If he does so, his bowing is complete. And when one of you prostrates, let him say in his prostration, 'Glory be to my Lord, the Most High,' three times. If he does so, his prostration is complete. That is the minimum."
حدثنا أبو بكر بن خلاد الباهلي حدثنا وكيع عن ابن أبي ذئب عن إسحق بن يزيد الهذلي عن عون بن عبد الله بن عتبة
قال رسول الله ﷺ إذا ركع أحدكم فليقل في ركوعه سبحان ربي العظيم ثلاثا فإذا فعل ذلك فقد تم ركوعه وإذا سجد أحدكم فليقل في سجوده سبحان ربي الأعلى ثلاثا فإذا فعل ذلك فقد تم سجوده وذلك أدناه
Its isnad is daif. Abu Dawud narrated it in the Book of Prayer, chapter on the measure of ruku and sujud, hadith 886, from the hadith of Ibn Abu Dhib, with this wording, and he said this is mursal, Awn did not meet Abdullah. Tirmidhi said its isnad is not connected, Awn did not meet Ibn Masud, hadith 261. And Ishaq bin Yazid is unknown (Taqrib).