Are human beings eternal in the Afterlife, or is their existence there contingent upon Allah's will? And what is the Islamic belief regarding this matter?

Allah has decreed that this world shall perish and die, after which He will resurrect His servants for accountability. They will then divide into two groups: the people of Paradise, who will abide therein forever, and the people of Hell, who are disbelievers, and will abide therein forever. Quranic verses and authentic Prophetic traditions have affirmed this eternal abiding, such as His saying, the Most High: ﴿But those who believe and do righteous deeds – We will admit them to gardens beneath which rivers flow, abiding eternally therein forever﴾ [An-Nisa: 57], and His saying: ﴿Indeed, those who disbelieved and committed wrong – never will Allah forgive them, nor will He guide them to a path except the path of Hell, abiding eternally therein forever﴾ [An-Nisa: 169]. The texts also clarify that the people of Hell will neither die therein nor live a good life, and that death will be slaughtered after the people of Paradise enter Paradise and the people of Hell enter Hell, signaling an eternity free from death.