Tafsir of Al-Teen 95:5

"Then We returned him to the lowest of the low," [the particle] thumma (then) denotes either a sequence in time or a sequence in rank.

Radd (returning/rendering) is either in the sense of 'making,' in which case it takes two objects whose origin is the subject and predicate, as in the saying: "And He turned their black hair white, and turned their white faces black." Thus, asfal (the lowest) is a second object for it here. The meaning is: "Then We made him one of the people of the Fire, who are uglier than everything ugly and lower than everyone low in nature and constitution, because he did not conduct himself according to the qualities upon which We created him."

It is also possible that radd implies a change of state, and is thus transitive to only one object, with asfal being a circumstantial qualifier (hal) for the object. That is: "We returned him while he was in a state of being the ugliest in form and the most distorted in creation," referring to the people of the Fire.

Or, radd is used in its well-known sense, with asfal being in the accusative case due to the omission of a preposition (i.e., ila asfal). In this case, al-asfal is an attribute for a [suppressed] place, and al-safilin (the low/the lowest ones) refers to low places. That is: "We returned him to a place [that is] the lowest of low places," which is Hell, or the lowest abyss of the Fire. An objection to this is that it is pluralized as an adjective for rational beings, and claiming it is for the sake of the [rhyme] sequence or treating [places] as rational beings is not something to be inclined toward. Perhaps the most appropriate view, in that case, is that it refers to: "To a place lower than those who are low among the dwellers of the [various] levels of Hell."

'Ikrimah, al-Dahhak, al-Nakha'i, and Qatadah (in one narration) said the intent is his return to old age and the weakening of [his] outward and inward faculties. That is: "Then We returned him—after that straightening and beautification—to the lowest of those who are low in terms of beauty of form and shape, as We reversed his creation. His back became bent after having been upright, his hair turned white after having been black, his skin wrinkled after having been smooth and delicate, his hearing and sight failed after they had been sharp, and everything about him changed; his walking became shuffling, his voice faint, his strength weakness, and his vigor senility."

The verse, according to this, is analogous to the saying of the Exalted: "Then We returned him to the lowest of life," and His saying: "And he whom We grant long life, We reverse him in creation." This is considered in terms of the [human] species, so it does not necessitate that every individual becomes like this. Regarding the parsing of asfal, the aforementioned ways are not hidden.

Then, the obvious meaning indicated by the context is the state of the disbeliever on the Day of Resurrection, that he will be in the ugliest and most grotesque form after having been in the best and most wondrous form, due to his lack of gratitude for that blessing and his failure to act according to its requirements. The interpretation [of old age] mentioned earlier does not fit well with this, and from this, it was said that it is contrary to the apparent meaning. The apparent meaning is what aligns with that [the context of the Day of Resurrection], as is narrated from al-Hasan, Mujahid, Abu al-'Aliyah, Ibn Zayd, and also Qatadah. 'Abdullah [ibn Mas'ud] recited it as al-safilin (the low ones) with the definite article al-.