﴿ ءَاخِذِينَ مَآ ءَاتَىٰهُمْ رَبُّهُمْ ۚ إِنَّهُمْ كَانُوا۟ قَبْلَ ذَٰلِكَ مُحْسِنِينَ ﴾

“enjoying all that their Sustainer will have granted them [because], verily, they were doers of good in the past:”

receiving ākhidhīna is a circumstantial qualifier referring to the person of the predicate of inna ‘truly’ what their Lord has given them of reward for indeed formerly before their entering Paradise they had been virtuous in the world.