Why were Old Testament believers not ready for God's presence before the cross?
Old Testament believers were not ready for God's presence because their sins had not been atoned for by the blood of Christ. Animal sacrifices could not remove sin's stain. Though saved for eternity, they went down to paradise, not heaven, until Christ's atoning work was accomplished.
Les explains that before the cross, from Adam onward, believers lived and died and went down to paradise, with only Enoch and Elijah as God's exceptions. They could not go to heaven because the atoning blood of Christ is the only thing that would remove the stain of sin. Animals' blood could not take it away. So these Old Testament believers were saved for eternity, but they were not ready for God's presence because their sins had not been atoned for by the blood of Christ. Therefore they went down to paradise. The context also describes Hades or hell as a place with a great gulf fixed, with torment on one side and paradise on the other. The lost from all ages go into the torment side. When the thief was told, "Today thou shalt be with me in paradise," Christ was speaking of the centermost part of the earth, where He would be three days and three nights. Paul puts his stamp of approval on this teaching.