"Indeed, Allah does not do injustice," meaning: He does not diminish, "even by the weight of an atom," that is: the weight of an atom (dharr).
Muhammad said: It is said: "This is according to the weight (mithqal) of this," meaning: according to its weight. "And if it is a good deed, He multiplies it, and gives from Himself," meaning: He bestows from His presence.
Muhammad said: Whoever reads it as "hasanatun" (a good deed) in the nominative case (raf'), the meaning is: and if a good deed occurs.