فَمَن يَعْمَلْ مِثْقَالَ ذَرَّةٍ خَيْرًا يَرَهُۥ Qur’an Az-Zalzalah (99:7)Faman yaAAmal mithq a la th arratin khayran yarah u
Zarrat: the weight of an atom, the smallest living weight an ordinary man can think of. Figuratively the subtlest form of good and evil will then be brought to account, and it will be done openly and convincingly: he "shall see it".