Hadith: The Prophet (may Allah's peace and blessings be upon him) did not offer a prayer after the revelation of {When there comes Allah’s help and the conquest} [Surat an-Nasr: 1] except that he would say therein: "Subhānaka Rabbana wa bihamdik, Allāhumma ighfir li (Glory and praise be to You, our Lord. O Allah, forgive me)

عَنْ عَائِشَةَ أُمِّ المُؤْمِنينَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ:
مَا صَلَّى النَّبِيُّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ صَلاَةً بَعْدَ أَنْ نَزَلَتْ عَلَيْهِ: {إِذَا جَاءَ نَصْرُ اللَّهِ وَالفَتْحُ} [النصر: 1] إِلَّا يَقُولُ فِيهَا: «سُبْحَانَكَ رَبَّنَا وَبِحَمْدِكَ اللَّهُمَّ اغْفِرْ لِي». وعَنْها قَالَتْ: كَانَ رَسُولُ اللهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ يُكْثِرُ أَنْ يَقُولَ فِي رُكُوعِهِ وَسُجُودِهِ: «سُبْحَانَكَ اللهُمَّ رَبَّنَا وَبِحَمْدِكَ، اللهُمَّ اغْفِرْ لِي» يَتَأَوَّلُ الْقُرْآنَ.
[صحيح] - [متفق عليه] - [صحيح البخاري: 4967]

‘Ā’ishah, Mother of the Believers, (may Allah be pleased with her) reported:
The Prophet (may Allah's peace and blessings be upon him) did not offer a prayer after the revelation of {When there comes Allah’s help and the conquest} [Surat an-Nasr: 1] except that he would say therein: "Subhānaka Rabbana wa bihamdik, Allāhumma ighfir li (Glory and praise be to You, our Lord. O Allah, forgive me)".
[Authentic hadith] - [Narrated by Bukhari & Muslim] - [Sahih Bukhari - 4967]

Explanation

‘Ā’ishah, Mother of the Believers (may Allah be pleased with her), informs that upon the revelation of {When there comes Allah’s help and the conquest} to the Prophet (may Allah's peace and blessings be upon him), he complied with the command in the Qur’an and hastened to obey the command of Allah Almighty in His saying: {Then glorify the praise of your Lord, and ask His forgiveness}. Therefore, he used to frequently say in his Rukū‘ (bowing) and Sujūd (prostration) during the prayer, "Glory be to You," and may You be Exalted above any deficiency that does not befit You. "And praise, O Allah, our Lord," praise that is rightfully due to You for the perfection of Your essence, attributes, and actions. "O Allah, forgive me" and erase and overlook my sin.