Tafsir of Al-Kahf 18:29

{And say, "The truth is from your Lord."} "The truth" (al-ḥaqq) is the predicate of an omitted subject. The meaning is: The truth has come, and the excuses have been removed. Nothing remains but your own choice to take either the path of salvation or the path of destruction.

The imperative form is used to denote the act of giving a choice, for when one is empowered to choose whichever he wills, it is as if he is commanded to choose between the two paths.

{...its walls will encompass them} The fire surrounding them is likened to a surādiq (canopy/enclosure), which is the partition placed around a tent. A "surādiq-ed" house is one that has such an enclosure. It is also said: It is smoke that surrounds the disbelievers before they enter the Fire. Others say: It is a wall of fire that encircles them.

{...they will be given water like molten copper} This is like the saying: "...and they were met with the sharp blade." There is mockery in this. Al-muhl is that which has been melted from the minerals of the earth. It is also said: It is the dregs of oil.

{...which will scald their faces} When it is brought near to be drunk, the face is scalded by its heat. According to the Prophet (peace be upon him), it is like the dregs of oil; when it is brought near to him, the skin of his face falls off.

{Wretched is the drink, and evil is the resting place} Murtafaqan (resting place) is derived from mirfaq (elbow/support). This is used to correspond to the verse: {...and good is the resting place} (Al-Kahf: 31). Otherwise, there is no comfort or reclining for the people of the Fire, unless it is taken from the saying: I remained awake, spending the night reclining, As if in my eyes there is bitter aloe, slaughtered.

{Indeed, those who have believed and done righteous deeds - indeed, We will not allow to be lost the reward of any who did well in deeds. Those will have gardens of perpetual residence; beneath them rivers will flow. They will be adorned therein with bracelets of gold and will wear green garments of fine silk and brocade, reclining therein on adorned couches. Excellent is the reward, and good is the resting place.}