Sahih al-Bukhari, Book 10, Hadith 212 (In-Book) ⓘ
Narrated `Aisha: The Prophet used to say frequently in his bowing and prostrations "Subhanaka l-lahumma Rabbana wa bihamdika, Allahumma ghfir li" (Exalted [from unbecoming attributes] Are you O Allah our Lord, and by Your praise [do I exalt you]. O Allah! Forgive me). In this way [??] he was acting on what was explained to him in the Holy Qur'an.
حَدَّثَنَا مُسَدَّدٌ، قَالَ حَدَّثَنَا يَحْيَى، عَنْ سُفْيَانَ، قَالَ حَدَّثَنِي مَنْصُورٌ، عَنْ مُسْلِمٍ، عَنْ مَسْرُوقٍ، عَنْ عَائِشَةَ ـ رضى الله عنها ـ أَنَّهَا قَالَتْ كَانَ النَّبِيُّ صلى الله عليه وسلم يُكْثِرُ أَنْ يَقُولَ فِي رُكُوعِهِ وَسُجُودِهِ " سُبْحَانَكَ اللَّهُمَّ رَبَّنَا وَبِحَمْدِكَ، اللَّهُمَّ اغْفِرْ لِي " يَتَأَوَّلُ الْقُرْآنَ.
also referenced under: Hadith 817 (DarusSalam) & Volume 1, Book 12, Hadith 781 (USC-MSA)