Tafsir of An-Nahl 16:84

{ A witness } Their prophet, who will testify for them and against them regarding faith and belief, or disbelief and denial.

{ Then, permission will not be granted to those who disbelieved } To offer excuses. The meaning is that they have no argument. The withholding of permission indicates that they possess neither argument nor excuse. This is also the view of al-Ḥasan.

{ Nor will they be asked to repent } They will not be asked to seek satisfaction [from God]. That is, it will not be said to them, "Seek to satisfy your Lord," because the Hereafter is not a place for deeds.

If you ask: What is the meaning of "then" (thumma) here? I say: Its meaning is that after the testimony of the prophets, they are afflicted with something even more severe: they are prevented from speaking, and no permission is granted to them to present an excuse or offer an argument.

The accusative case of "the Day" (al-yawm) is governed by an omitted verb, estimated as: "And remember the Day We shall raise," or "On the Day We shall raise, they fell into what they fell into." Likewise, when they see the punishment, it comes upon them suddenly and weighs heavily upon them.

{ It will not be lightened for them, nor will they be reprieved } This is like His saying: “Rather, it will come upon them suddenly and bewilder them” (Al-Anbiyāʾ: 40).

{ And when those who associated partners with God see their partners, they will say, "Our Lord, these are our partners whom we used to invoke besides You." But they will throw the statement back at them, "Indeed, you are liars." * And they will offer to God on that Day [their] submission, and lost from them will be what they used to invent. }