Al-Mutaffifin 83:17 - Linguistic Miracle

Thumma, it is said to them, “This is what you used to consider a lie.”

Thumma again means two things which have been explained above.

The words به seem extra. As a matter of fact, even without this phrase, the meaning remains complete. There are two possibilities here.

Firstly, its use is subject to what is being denied. If what is being denied is the person himself, Ba is omitted. Whereas, if the object of denial is what that person is saying, then Ba is used. Since they are rejecting Hellfire, Ba was used.

Secondly, it could be that the Ba is ( سببية causal). You used to consider the messengers

a lie because of this punishment. Because the messengers warned you of this punishment, you called them a liar. I go by this because this ties in with what has come before in verse 14. They used to deny justice being delivered to people for their actions because their sins and evil deeds had covered up and rusted their hearts. Now, they deny messengers because they confirm and preach this very thing they deny. So one thing leads to another. They commit evil deeds, which blacken their hearts and suck the life out of them. This leads them to deny justice being delivered to people. Now that they believe justice is false, anyone who believes justice to be true, will be deemed a liar by them because he is affirming a false thing in their opinion.

Allah is pointing out the root cause to these people, which He also highlighted in the last verse by using the genitive construction. The main cause of your wickedness are your actions. Redeem yourselves, undo the wrong that you did to people, to restore life and strength to your hearts. Once you do this, when your hearts come back to life, you will recognize the truth of this message and of judgment day. If you don’t do this, then the occasion on which you become certain of judgment day, will be when you see it for yourselves, by which time it will be too late. The fire waits for you as a just recompense for your actions if you do not repent and undo your wrongs.