إِنَّ ٱلَّذِينَ ءَامَنُوا۟ وَعَمِلُوا۟ ٱلصَّـٰلِحَـٰتِ إِنَّا لَا نُضِيعُ أَجْرَ مَنْ أَحْسَنَ عَمَلًا
Innal lazeena aamanoo wa 'amilus saalihaati innaa laa nudee'u ajra man ahsana 'amalaa
As for those who believe and do righteous deeds — indeed, we do not let the reward of anyone who does good go to waste.
Arabic opens this line with a subject and then never gives it a predicate: a fresh sentence starts where the completion should be, so the promise widens from those particular believers to anyone at all who acts well. Ahsana 'amalan comes back here from 18:7, where the adornment of the earth was set as a test of who would act best. The terms of the test return as the thing guaranteed against loss.