They will go between it and Hamim An!
meaning, they will sometimes be punished with fire and they will sometimes be given Hamim which is a drink like molten copper tearing their intestines and internal organs,
إِذِ الاٌّغْلَـلُ فِى أَعْنَـقِهِمْ والسَّلَـسِلُ يُسْحَبُونَ
فِى الْحَمِيمِ ثُمَّ فِى النَّارِ يُسْجَرُونَ
When the iron collars will be rounded over their necks, and the chains, they shall be dragged along, in the Hamim, then they will be burned in the Fire. (40;71-72)
Allah said,
انٍ
(An), meaning hot, due to the fierce and intense heat that is impossible to bear.
Ibn Abbas said;
يَطُوفُونَ بَيْنَهَا وَبَيْنَ حَمِيمٍ انٍ
(They will go between it and Hamim An!),
"That has reached the ultimate temperature and boiling fiercely."
Similar was said by Mujahid, Sa`id bin Jubayr, Ad-Dahhak, Al-Hasan, Ath-Thawri and As-Suddi.
Qatadah also commented,
"Its boiling started when Allah created the heavens and the earth!"
Muhammad bin Ka`b Al-Qurazi said,
"The (disobedient) servant will be seized by the forehead and stirred in that boiling water until his flesh melts and only the bones and the eyes in his head remain.
This is the meaning of Allah's statement,
فِى الْحَمِيمِ ثُمَّ فِى النَّارِ يُسْجَرُونَ
In the Hamim, then they will be burned in the Fire. (40;72)
And Al-Hamim Al-An means hot."
There is another report from Al-Qurazi;
حَمِيمٍ انٍ
(Hamim An) that it means "prepared. "
This is also the view of Ibn Zayd.
And saying that it means "prepared" does not contradict the first report from Al-Qurazi which says that it means hot, for Allah said;
تُسْقَى مِنْ عَيْنٍ ءَانِيَةٍ
They will be given to drink from a spring, Aniyah. (88;5)
which means severe unbearable heat,
and His saying;
غَيْرَ نَـظِرِينَ إِنَـهُ
not to wait for it to be prepared, (33;53)
which means properly cooking and preparing it.
So His saying;
حَمِيمٍ انٍ
(Hamim An), Hamim, that is very hot.
Surely, punishing the disobedient criminals as well as favoring those who had Taqwa, is from Allah's grace, mercy, justice, compassion and kindness for His creatures. His warnings against His torment and punishment, such as mentioned in these Ayat, should encourage all creatures to abandon the Shirk and disobedience they engage in, and this is why Allah reminded them of this favor;
فَبِأَيِّ الَاء رَبِّكُمَا تُكَذِّبَانِ