Tafsir of Al-Anbiya' 21:47

{The scales} are described as {of justice}—which means equity—as a hyperbole, as if the scales themselves are justice personified. Or, it is by way of omitting the genitive (idafa), meaning: "possessors of justice."

The lam (preposition) in {for the Day of Resurrection} is like the one in your saying: "I came to him for five nights having passed from the month." From this is the verse of al-Nabigha: I traced the signs of it and recognized them, After six years, and this year is the seventh.

It is also said: It means "for the people of the Day of Resurrection," i.e., for their sake.

If you ask: What is meant by "setting up the scales"? I say: There are two opinions:

1. It refers to the preparation of an accurate reckoning and recompense according to deeds, with justice and fairness, such that He does not wrong His servants by the weight of an atom. This is represented by the setting up of scales to weigh the things to be weighed.
2. That He sets up literal scales and weighs the deeds with them. Al-Hasan said: It is a scale with two pans and a tongue (pointer). It is narrated that David (peace be upon him) asked his Lord to show him the scale. When he saw it, he fainted. When he recovered, he said: "My God, who is able to fill its pan with good deeds?" He replied: "O David, when I am pleased with My servant, I fill it with a single date."

If you ask: How can deeds be weighed when they are mere accidents (non-substances)? I say: There are two opinions:

1. The scrolls of deeds are weighed.
2. Bright, radiant jewels are placed in the pan of good deeds, and dark, gloomy jewels are placed in the pan of evil deeds.

{The weight of a mustard seed} is read as kana (the verb "to be") in the sense of "existence" (al-tamma), like His saying: "And if he is in straitened circumstances."

Ibn Abbas and Mujahid read: {We brought it} (atayna biha), which is a reciprocal form (mufa'ala) of "coming," meaning recompense and reward, because they came to Him with their deeds, and He came to them with the recompense. Humayd read: {We rewarded with it} (athabna biha) from thawab (reward). In the codex of Ubayy, it is: {We brought it} (ji'na biha).

The pronoun for "weight" (mithqal) is treated as feminine because it is annexed to "seed" (habba), like their saying: "Some of his fingers went" (dhahabat ba'du asabi'ihi), meaning: "We brought them both."

{And We certainly gave Moses and Aaron the Criterion, and a light, and a reminder for the righteous.}