A flood of false doctrine has lately broken in upon us. Men are beginning to tell us “that God is too merciful to punish souls for ever...that all mankind, however wicked and ungodly...will sooner or later be saved.” We are to embrace what is called “kinder theology,” and treat hell as a pagan fable... This question lies at the very foundation of the whole Gospel. The moral attributes of God, His justice, His holiness, His purity, are all involved in it. The Scripture has spoken plainly and fully on the subject of hell... If words mean anything, there is such a place as hell. If texts are to be interpreted fairly, there are those who will be cast into it... The same Bible which teaches that God in mercy and compassion sent Christ to die for sinners, does also teach that God hates sin, and must from His very nature punish all who cleave to sin or refuse the salvation He has provided.

~ J.C. Ryle

Read this article: The Positive and Explicit Nature of Christ’s Teaching Concerning Eternal Punishment