ثُمَّ لَا يَمُوتُ فِيهَا وَلَا يَحْيَىٰ
ثُمَّ in Arabic can state two things: an interval of time (then, after a period has passed) and an interval of rank (and what is more, moreover).
Here the second sense works as well. The verse does not merely set up an order of time; it makes a grading: to enter the fire is one thing — and what is more, there is neither dying there nor living.
The verse, that is, says something heavier than the one before it, and thumma carries this increase of weight.
The expected order would have been the reverse — a being first lives, then dies. The verse breaks this order.
The reason lies in the context: what is wanted is death. The verse answers first what is wanted. The Qurʾān records this wanting explicitly elsewhere:
"They will call out: O Mālik! Let your Lord make an end of us. He will say: You are to remain" (al-Zukhruf 43/77).
"Death is not decreed for them, that they might die" (Fāṭir 35/36).
"Whoever comes to his Lord as a guilty one, for him is the Fire; there he neither dies nor lives" (Ṭāhā 20/74).
The same expression, the same order, the same two verbs. The difference between the two verses lies in the context: in Ṭāhā the description mujrim (the guilty one), in al-Aʿlā the description al-ashqā.
What is death? It is the ending of a thing. However bad it may be, death is a bringing to an end. What a human being holds on to even in the hardest situations is the knowledge that the situation will end.
What is life? In the Qurʾān's concept of life there are several elements: movement, perception, and — most important of all — the possibility of change. The condition of a living being can change; where it is today it may not be tomorrow.
The verse does away with both definitions. There is neither an end nor change. What remains is a perpetual present.
And exactly here a contrast is set up with the fourth and fifth verses of the sūra. There was a cycle there: the pasture comes out, dries, becomes scum. Every stage of the cycle passes into the next. To come to an end is the law of this world and — however painful it may be — it is a relief.
The thirteenth verse describes a place where that law does not operate. I record this as my own reading; it is I who establish the contrast between the two verses.
This verse is one of the texts used in the debates about the everlastingness of the punishment of the Fire. The detail of that debate — the duration of the punishment, for whom it is everlasting, the scope of the word khulūd — has a long history in Islamic thought and goes beyond the limits of this text.
What I must state here is this: the verse states no duration. The expression "he neither dies nor lives" describes a state, not how long that state will last. I do not use the verse as evidence for any side of the debate.