All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The past tense in this verse and in all the previous ones in Soorat At-Takweer (chapter no. 81) denote the meaning of the future, and the past tense was used to reflect the absolute certainty of their occurrence.
Ibn ‘Ashoor said in At-Tahreer and At-Tanweer:
“The past tense in the twelve conditional sentences that list the conditions of “if” denote the future, indicating the fact that these conditions shall inevitably be fulfilled.” [End of quote]
Al-Qurtubi said in his Tafseer:
“The particle Itha (if) followed by a sentence in the past tense denotes the future because it acts as a conditional particle.” [End of quote]
However, this does not mean that Hellfire will not exist or will not be burning except on the Day of Resurrection. It rather means that its flames and fierceness shall increase.
Isma‘eel Haqqi said in his Tafseer book Rooh Al-Bayan: “The meaning of setting Hellfire ablaze here means that its flames and fierceness shall increase, not that it would come into existence for the first time. This refutes the claim that Hellfire has not been created yet because the verse indicates that setting it ablaze is conditioned to the Day of Resurrection because its flames and fierceness shall increase.” [End of quote]
The Hanafi scholar Ibn Abu Al-‘Izz said in his explanation of At-Tahawiyah: “Ahlus-Sunnah Wal-Jama‘ah agreed that Paradise and Hellfire are created and existent now, and this belief continued to be held by Ahlus-Sunnah Wal-Jama‘ah until a group from the Mu‘tazilah and Qadariyyah sects denied their existence and claimed that Allah, The Exalted, shall create them on the Day of Judgment!” [End of quote]
Allah knows best.