Tafsir of Al-Mulk 67:25

{But when they saw it} The pronoun refers to the promise. Al-zulfa means proximity; its accusative case is due to it being a state (ḥāl) or an adverbial of place (ẓarf). That is: they saw it as being near, or as a place that is near.

{The faces of those who disbelieved were darkened} Meaning: The sight of the promise caused their faces to become wretched, as gloom, eclipse, and darkness covered them. They became grim-faced, just as the face of one who is being led to execution or presented with some form of torment appears.

{And it was said} The ones saying this are the guards of Hell (al-zabāniyah).

{This is that which you used to call for} Tadʿūn is in the form taftaʿilūn derived from duʿāʾ (calling/supplication), meaning: you requested it and sought to hasten it. It is also said to be derived from daʿwā (claim), meaning: because of it, you used to claim that you would not be resurrected. It is also recited as tudʿawn (you are called to it).

It is narrated that one of the ascetics recited this verse at the beginning of the night during his prayer, and he continued to repeat it while weeping until the call for the dawn prayer was made. By my life, it is indeed a terrifying warning for one who envisions that state and contemplates it.

{Say, "Have you considered: if Allah should destroy me and those with me or have mercy upon us - who can protect the disbelievers from a painful punishment?"}