Christ was without sin and he fully paid the price of our redemption on the cross. So if Christ's suffering was finished on the cross, why did His human soul descend into hell?
First we must confer with Saint Thomas Aquinas and other saints and doctors who divide hell (infernus) into four abodes:
- Purgatory (abode of those being purified)
- Limbo of the Fathers (abode of the Old Testament faithful - now it's empty)
- Limbo of the Children (abode for unbaptized children under the age of reason)
- Gehenna (abode of the damned)
Usually when we speak of "hell" we mean "the fires of hell" or Gehenna. At STh III, q. 52, a. 2, Saint Thomas Aquinas is clear that Christ did not descend into Gehenna. (For those interested in such things, Hans Urs Von Balthasar stands if full contradiction to Catholic tradition on this point.)
Christ's soul descended to the Limbo of the Fathers, also known as Abraham's Bosom:
“And it came to pass that the beggar died and was carried by the angels into Abraham’s bosom. And the rich man also died: and he was buried in hell.” (Luke 16:22, D-R)
In the Old Testament, the gates of Heaven were not open to human souls. So the faithful in the Old Testament remained in the Limbo of the Fathers until the passion and death of Christ - those from Adam till even the thief on the cross.
Now Saint Thomas Aquinas teaches that since the Old Testament faithful did not have the sacraments, that Christ's descent into the inferno was for them as the sacraments are to us:
Hence, as the power of the Passion is applied to the living through the sacraments which make us like unto Christ's Passion, so likewise it is applied to the dead through His descent into hell. On which account it is written (Zechariah 9:11) that "He sent forth prisoners out of the pit, in the blood of His testament," that is, by the power of His Passion.
So Abraham was not baptized, but he did receive the efficacy of baptism by the descent of Christ into the Limbo of the Fathers. Thus, the doctrine of Christ's descent into Hell solves many theological difficulties: the lack of sacramental efficacy in the Old Law, the salvation of people before Christ, and the distinction of abodes in hell.