They will abide therein Ahqab.
meaning, they will remain in it for Ahqab, which is the plural of Huqb.
Huqb means a period of time.
Khalid bin Ma`dan said,
"This Ayah, and the Ayah,
إِلاَّ مَا شَأءَ رَبُّكَ
(except your Lord wills.11;107), both refer to the people of Tawhid.
Ibn Jarir recorded this statement.
Ibn Jarir also recorded from Salim that he heard Al-Hasan being asked about Allah's statement,
لَّـبِثِينَ فِيهَأ أَحْقَاباً
"In reference to Ahqab, it has no specific amount of time other than its general meaning of eternity in the Hellfire. However, they have mentioned that the Huqb is seventy years, and every day of it is like one thousand years according to your reckoning (in this life)."
Sa`id reported from Qatadah that he said, "Allah says,
لَّـبِثِينَ فِيهَأ أَحْقَاباً
And it is that which has no end to it. Whenever one era comes to an end, a new era follows it. It has been mentioned to us that the Huqb is eighty years."
Ar-Rabi` bin Anas said,
لَّـبِثِينَ فِيهَأ أَحْقَاباً
"No one knows how much time this Ahqab is, except for Allah, the Mighty and Sublime. It has been mentioned to us that one Huqb is eighty years, and the year is three hundred and sixty days, and each day is equivalent to one thousand years according to your reckoning (in this life)."
Ibn Jarir has recorded both of these statements.
Allah's statement;
لاَّا يَذُوقُونَ فِيهَا بَرْدًا وَلَا شَرَابًا