The concept of generous reward (ajr karim)

تَحِيَّتُهُمْ يَوْمَ يَلْقَوْنَهُۥ سَلَـٰمٌ ۚ وَأَعَدَّ لَهُمْ أَجْرًا كَرِيمًا

Their greeting the Day they meet Him will be, "Peace." And He has prepared for them a noble reward.