The physically dead before the cross were held in captivity because they could not enter into Paradise until after their full and complete redemption was fulfilled at the cross. This part you may know very well, so I won't belabor the point.
So, some questions can come up about what comes after the cross for them. I'm sure we can agree that they are now, although not before, in paradise with Christ. They do not yet have their glorified bodies, but will receive those immediately before the rest of those who are alive at the point of the rapture, since we are told that the dead in Christ rise first, and then the living at the point of the rapture.
Given that the Lord declared to us in His word that one must be born again to enter into the Kingdom of God, it follows that the OT saints received their new birth at the point of the cross. I'm not saying that's a hard core fact, but it seems that their final and complete redemption was at or after the Jesus declared "It is finished."
Bottom line, of course, is that no matter when they were born again, we are going to one day be gathered up with them in the clouds with Christ, and to be with Him thereafter for eternity.
There may be some out there who think they know exactly when the new birth of the OT saints took place, and I won't take issue with them since we are not told that sliver of information...possibly because the Lord might say to us, "What is that to you. You go and be about My business."
I'm thankful for the Lord's correction, because I need it so much of the time. The hinges and latch on the wood shed are pretty much worn out because of me. I'm just thankful the Lord is patient with those such as myself.
MM