His body was in the tomb but his spirit was on the grave/sheol.
In Hebrew, sheol is the place of darkness in which spirits of the dead go.
Without going too deep into theology, I want to show/remind you that God is not just concerned with the living but the dead also.
1 Peter 3:19 says that Jesus preached to the spirits in prison. Over 2 thousand years ago on a day like today, Jesus went into the grave to minister salvation to imprisoned spirits.
God does not want any sinner to perish (to die in their sin or be separated by eternal condemnation). But he wished that all would repent and receive eternal life.