The religious conservatives in Jesus’ day clearly believed in endless punishment. However, the words and phrases that both Josephus and Philo used to describe what the Pharisees and other groups at the time believed with regard to the fate of the wicked, are never found in the New Testament in connection with punishment.
Neither Jesus nor any of the other New Testament writers used the Greek terms translated as everlasting prison, eternal punishment, never-ceasing punishments, immortal punishment after death, and undying and never ending death.
Later, we’ll look specifically at what Jesus actually said about after-death punishment to show that the adjective He used really meant limited duration. And the noun denoted suffering resulting in correction.
— George W. Sarris, Heaven’s Doors: Wider Than You Ever Believed!, p. 33-34