(Imām Bukhārī narrates): Abū al-Walīd narrated to us, he said: Shu'bah narrated to us, from Thābit, he said:
Anas, may Allāh be pleased with him, used to describe for us the qualities of the prayer of the Prophet ﷺ: he used to pray, so when he raised his head from rukū', he would stand for so long that we would say: Perhaps he has forgotten.
حَدَّثَنَا أَبُو الْوَلِيدِ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنْ ثَابِتٍ، قَالَ كَانَ أَنَسٌ يَنْعَتُ لَنَا صَلاَةَ النَّبِيِّ صلى الله عليه وسلم فَكَانَ يُصَلِّي وَإِذَا رَفَعَ رَأْسَهُ مِنَ الرُّكُوعِ قَامَ حَتَّى نَقُولَ قَدْ نَسِيَ.
Reference: Sahih Al Bukhari 800