﴿ وَٱلَّذِينَ هُمْ عَلَىٰ صَلَوَٰتِهِمْ يُحَافِظُونَ ﴾

“and who guard their prayers [from all worldly intent].”

And who are watchful of their prayers may be read as plural salawātihim ‘their prayers’ or singular salātihim ‘their prayer’ observing them at their appointed times.