The basis of the doctrine that heaven was closed is in Genesis 3 and original sin; heaven is not opened to those in mortal sin, and all humanity was consigned to original, mortal sin until God showed His mercy in Christ. 1 Peter 3:18-20 plus 4:6 plus Ephesians 4:8-9 seems to imply that dead pre-Christians were kept in a sort of “prison” (known in the Old Testament as “Sheol”) until the resurrection of Christ; thereupon, Christ led them free into heaven.
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