Sunan Abi Dawud 1034
Narrated Abdullah ibn Buhaynah:
The Messenger of Allah (ﷺ) led us in prayer praying two rak'ahs. When he stood up and did not sit (at the end of two rak'ahs) the people stood up along with him. When he finished the prayer  and we expect him to give the salutation, he said: "Allah is most great." While sitting and made two prostrations before giving the salutation. Then he gave it.
حَدَّثَنَا الْقَعْنَبِيُّ، عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ عَبْدِ الرَّحْمَنِ الأَعْرَجِ، عَنْ عَبْدِ اللَّهِ ابْنِ بُحَيْنَةَ، أَنَّهُ قَالَ صَلَّى لَنَا رَسُولُ اللَّهِ صلى الله عليه وسلم رَكْعَتَيْنِ ثُمَّ قَامَ فَلَمْ يَجْلِسْ فَقَامَ النَّاسُ مَعَهُ فَلَمَّا قَضَى صَلاَتَهُ وَانْتَظَرْنَا التَّسْلِيمَ كَبَّرَ فَسَجَدَ سَجْدَتَيْنِ وَهُوَ جَالِسٌ قَبْلَ التَّسْلِيمِ ثُمَّ سَلَّمَ صلى الله عليه وسلم ‏.‏