Sahih al-Bukhari 6670
Sahih al-Bukhari · Book 83: Oaths and Vows · If someone does something against his oath due to forgetfulness
Narrated `Abdullah bin Buhaina:
حَدَّثَنَا آدَمُ بْنُ أَبِي إِيَاسٍ ، حَدَّثَنَا ابْنُ أَبِي ذِئْبٍ ، عَنِ الزُّهْرِيِّ ، عَنِ الأَعْرَجِ ، عَنْ عَبْدِ اللَّهِ ابْنِ بُحَيْنَةَ ، قَالَ صَلَّى بِنَا النَّبِيُّ صلى الله عليه وسلم فَقَامَ فِي الرَّكْعَتَيْنِ الأُولَيَيْنِ قَبْلَ أَنْ يَجْلِسَ، فَمَضَى فِي صَلاَتِهِ، فَلَمَّا قَضَى صَلاَتَهُ انْتَظَرَ النَّاسُ تَسْلِيمَهُ، وَسَجَدَ قَبْلَ أَنْ يُسَلِّمَ، ثُمَّ رَفَعَ رَأْسَهُ، ثُمَّ كَبَّرَ وَسَجَدَ، ثُمَّ رَفَعَ رَأْسَهُ وَسَلَّمَ.
Once Allah's Messenger (ﷺ) led us in prayer, and after finishing the first two rak`at, got up (instead of sitting for at-Tahiyyat) and then carried on with the prayer. When he had finished his prayer, the people were waiting for him to say Taslim, but before saying Tasiim, he said Takbir and prostrated; then he raised his head, and saying Takbir, he prostrated (SAHU) and then raised his head and finished his prayer with Taslim.