Does Paul include Old Testament saints in his statement that sins are atoned for by Christ's shed blood?
Yes. Paul’s argument includes the Old Testament saint, not only the New Testament believer. The Old Testament saint’s sins were now totally atoned for by virtue of the shed blood of Christ. Once the true atonement was accomplished, there was no reason to send people down into paradise.
Les explains that Paul is reminding us that the atonement by Christ’s shed blood was not limited to the New Testament believer. He is also bringing in the Old Testament saint, whose sins were now totally atoned for. Once the true atonement was accomplished, there was no reason to send people down into paradise; paradise was taken directly to heaven. Les also notes Paul’s constant emphasis that we have no righteousness of our own and nothing to barter, and that we must admit we are helpless and hopeless—that is when God steps in.