Your Prophet ﷺ, when bowing or prostrating, used to say, "Glory be to You and praise be to You. I seek Your forgiveness and turn to You in repentance."
كان نبيكم ﷺ إذا كان راكعا أو ساجدا قال: سبحانك وبحمدك أستغفرك وأتوب إليك.
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Tabarani related it in Al-Kabir (10/192) from Ahmad bin Khalid Halabi, who said, Abdullah bin Jafar Raqqi told us, Ubaydullah bin Amr told us, from Zayd bin Abu Unaysa, from Hammad, from Abu Duha, from Masruq, from Abdullah bin Masud, who said, and then he mentioned it.Its chain is hasan because of Hammad, who is Ibn Abu Sulayman Kufi, for his hadith is hasan when there is no objectionable element in it, and this is such a case.The hadith has another route, which is what Imam Ahmad related (3683, 3719, 3745) through several chains from Abu Ishaq Sabi, from Abu Ubayda, from Abdullah bin Masud, who said, "When "When the help of Allah comes and victory" [Nasr 110:1] was revealed to the Messenger of Allah ﷺ, he would often say, whenever he recited it and bowed in ruku, 'Glory be to You, O Allah our Lord, and praise be to You. O Allah, forgive me, for You are the Ever-Returning, the Merciful,' three times."Its chain is disconnected, because Abu Ubayda, who is the son of Abdullah bin Masud, never heard directly from his father.