Luther’s Easter sermon from 1533, which teaches that Christ’s descent into hell is an article of faith. Reason cannot grasp it. God has only seen fit to reveal that Christ has descended, not for punishment or for additional suffering, but in victory. His descent is the beginning of His exaltation.
And what’s more, God reveals the purpose of His descent: to proclaim. Jesus descends into hell to preach the first Easter sermon. Luther says to believe it like the old pictures portray it: Christ as a mighty conqueror, holding a banner, with death and Satan under His feet (1 Corinthians 15:25-28). By His death, He has destroyed the power of death, and by His resurrection, He has opened for us the way of everlasting life. His descent means our resurrection.
“So think on this and say it out loud whenever you say the creed — as if you yourself are beating down Satan under your feet with these words — He descended into hell. Because in Baptism you are joined with Christ’s death and His resurrection and made part of His body, which means that His foot that holds down Satan is also your foot and His victory over death is your victory over death.”
Paul Althaus “Theology of Luther”.