Tafsir of Ash-Shura 42:26

{And He answers those who believe} Meaning: He answers for them. The preposition lam (لـ) is omitted here, just as it is omitted in His saying: {And when they measure for them} (Al-Mutaffifin: 3).

It means: He rewards them for their obedience and increases them beyond that reward out of His grace. Or, it means: when they call upon Him, He answers their supplication, grants them what they requested, and gives them more than what they asked for.

It is also said: "The answering" refers to their action—meaning they answer Him with obedience when He calls them to it. {And He increases them}—this is {from His bounty}—beyond their reward.

Sa'id ibn Jubayr said: This refers to their action; they answer Him when He calls them.

It is narrated that Ibrahim ibn Adham was asked: "Why is it that we call upon God, yet we are not answered?" He replied: "Because He called you, and you did not answer Him." Then he recited: {And Allah invites to the Home of Peace} (Yunus: 25), and {And He answers those who believe}.

{And if Allah were to extend provision for His servants, they would commit tyranny throughout the earth. But He sends down in a measure what He wills. Indeed, He is, of His servants, Acquainted and Seeing.}