فَمَن يَعْمَلْ مِثْقَالَ ذَرَّةٍ خَيْرًا يَرَهُۥ
Famaiy ya'mal mithqala zarratin khai raiy-yarah
whoever has done an atom's weight of good will see it,
Dharra names the smallest thing the eye can pick out, a mote in a shaft of light or the least of ants, so the measure set here sits at the bottom limit of what counts as a quantity. Elsewhere the word belongs to God's knowledge, where nothing of that weight escapes him; here it is turned around and applied to the record a person carries. The verse after this is identical but for one word.