Tafsir of Al-A'raf 7:42

(And those who believed), meaning in Our signs and did not deny them, (and did righteous deeds), (and were not arrogant toward them).

(We do not burden any soul except with that within its capacity), meaning that which it can perform easily, without being strained or distressed by it. This sentence is an interruption (parenthetical) placed between the subject—which is the relative pronoun "those who"—and the predicate, which is the sentence (Those are the companions of Paradise). This is intended to encourage [the believer] to acquire that which leads to everlasting bliss, by clarifying the ease of attaining it and the simplicity of its acquisition.

It has been said: The meaning is "We do not burden any soul except with that which yields for it sa'ah (expansion/abundance)," meaning a Paradise whose breadth is the heavens and the earth. This, however, is contrary to the apparent meaning, even if the verse, when interpreted this way, is not devoid of encouragement.

It is also permitted that the demonstrative pronoun ("Those") be a substitute for the relative pronoun ("those who"), and that what follows it is the predicate of the subject. The reference to distance (bud) contained in the demonstrative pronoun is to signal the loftiness of their rank in virtue and honor.

It is further permitted that the sentence (We do not burden...) be the predicate of the subject, with the assumption of a returning pronoun (an ellipsis), meaning "of them."

And His saying, Exalted is He, (they will abide therein eternally):

It is a circumstantial qualifier (hal) for (the companions of Paradise). It is also permitted that it be a circumstantial qualifier for (Paradise), as it contains a pronoun referring back to it, and the governing agent therein is the meaning of possession (idafa) or an implied preposition (lam).

It has been said: It is a predicate for "those" (the demonstrative), according to the view of whoever permits that. (Therein) is linked to (abiding eternally), and it precedes it in observance of the rhyme scheme.