"Eat and drink with happiness because of what you used to do."is similar to another of His statements,كُلُواْ وَاشْرَبُواْ هَنِييَاً بِمَأ أَسْلَفْتُمْ فِى الاٌّيَّامِ الْخَالِيَةِEat and drink at ease for that which you have sent on before you in days past! (69:24)meaning this is the just reward for your deeds; surely, all this is a favor from Allah and a reward from Him.Allah the Exalted said