he performed Salat with the Prophet, and that while he was bowing he would say: (Subhana Rabbiyal Azim); "Glorious is my Lord the Magnificent" and while prostrating: (Subhana Rabbiyal A'la) 'Glorious is my Lord the Most High.' And he would not recite an Ayah mentioning mercy, except that he would stop and ask (for mercy), and he would not recite an Ayah mentioning punishment, except that he would stop and seek refuge (with Allah from it). (Using translation from Tirmidhī 262)
أَنَّهُ صَلَّى مَعَ النَّبِيِّ ﷺ فَكَانَ يَقُولُ فِي رُكُوعِهِ سُبْحَانَ رَبِّيَ الْعَظِيمِ وَفِي سُجُودِهِ سُبْحَانَ رَبِّيَ الْأَعْلَى وَمَا مَرَّ بِآيَةِ رَحْمَةٍ إِلَّا وَقَفَ فَسَأَلَ وَلَا بِآيَةِ عَذَابٍ إِلَّا تَعَوَّذَ