Tafsir of As-Saffat 37:63

It is an ordeal and a punishment for them in the Hereafter, and a trial in this world. For when they heard that it [the Zaqqum tree] is in the Hellfire, they said, "How is that possible, when fire consumes trees?" Abu Jahl likewise spoke, mocking its nature and denying the linguistic implication, saying, "By God, we know of Zaqqum only as dates and butter." Thus, they were torn asunder in their belief. They did not know that He who has the power to create a creature that lives in the fire and finds pleasure in it, is all the more capable of creating a tree within the fire and preserving it from being consumed. For the fire does not burn except by His permission, or [alternatively] the burning occurs at the occasion of the fire, not by the fire itself.