Then Allah revealed the words:

إِنَّهَا شَجَرَةٌ تَخْرُجُ فِي أَصْلِ الْجَحِيمِ ﴿٦٤﴾

Verily, it is a tree that springs out of the bottom of Hell-fire.

meaning, it is nourished by the fire, for it was created from fire.''

Mujahid said: إِنَّا جَعَلْنَاهَا فِتْنَةً لِّلظَّالِمِينَ (Truly, We have made it (as) a trial for the wrongdoers).

Abu Jahl, may Allah curse him, said, "Zaqqum means dates and butter which I eat (Atazaqqamuhu).''

I say that the meaning of the Ayah is,

"We have told you, O Muhammad, of the tree of Zaqqum as a trial with which We test the people to see who will believe and who will disbelieve.''

This is like the Ayah:

وَمَا جَعَلْنَا الرُّءْيَا الَّتِى أَرَيْنَـكَ إِلاَّ فِتْنَةً لِّلنَّاسِ وَالشَّجَرَةَ الْمَلْعُونَةَ فِى القُرْءَانِ وَنُخَوِّفُهُمْ فَمَا يَزِيدُهُمْ إِلاَّ طُغْيَانًا كَبِيرًا

And We made not the vision which we showed you but a trial for mankind, and the accursed tree in the Qur'an. We warn and make them afraid but it only increases them in naught save great disbelief, oppression and disobedience to Allah. (17:60)

إِنَّهَا شَجَرَةٌ تَخْرُجُ فِي أَصْلِ الْجَحِيم

Verily, it is a tree that springs out of the bottom of Hell-fire.

means, its roots grow at the bottom of Hell.