Gehenna was closer to purgatory than hell.“Here is a law for you that will last for all time to come. Once a year you must pay for all the sin of the Israelites.”
Leviticus
Sins must be paid for because sin is breaking the law of God and if God ignores his own Law then he would be approving of sin. To ignore his own law would be to contradict his holy character from which the law is derived. But, God cannot ignore his own holy character.
Therefore, the Law must be upheld and carried out along with the punishments it contains. In Judaism the payment is with an annual animal sacrifice. In Christianity, the punishment is taken care of one of two ways, by Jesus on the cross that permanently pays for our sins or by the unbeliever in hell forever. Either way, the sins are paid for and the law is satisfied.
Zechariah 13:9 – “And I will bring the third part through the fire, and will refine them as silver is refined, and will try them as gold is tried: they shall call on my name, and I will hear them: I will say, It is my people: and they shall say, the Lord is my God.”