Q. How could the people in the Old Testament become righteous without the blood of Jesus? John 14:6 says “No one comes to the Father but through me.”
A. OT people become righteous in exactly the same way as NT people, by grace through faith in God. This is clearly explained in Rom 4:
• Rom 4:3, 6 What does Scripture say? “Abraham believed God, and it was credited to him as righteousness.” … David says the same thing when he speaks of the blessedness of the one to whom God credits righteousness apart from works.
• Rom 4:13 It was not through the law that Abraham and his offspring received the promise that he would be heir of the world, but through the righteousness that comes by faith.
• Rom 4:21-24 being fully persuaded that God had power to do what He had promised. This is why “it was credited to him as righteousness.” The words “it was credited to him” were written not for him alone, but also for us, to whom God will credit righteousness—for us who believe in Him who raised Jesus our Lord from the dead.
Note the following:
• Abraham believed God, and God credited righteousness to him apart from works.
• It was not through keeping the law, but by faith.
• This principle by receiving righteousness through faith is not just for Abraham alone, but for us who believe in Him as well.
No one comes to the Father except through Jesus. OT people looked forward to the cross. In God’s forbearance He had left the sins committed beforehand (up to the cross) unpunished (Rom 3:25). NT people look backward to the same once-for-all sacrifice of the Son making atonement for our sins. OT people may not know the Son as clearly as NT folks, but they knew and trusted the Father. Both are fully persuaded that God will fulfill what He promised. There is no difference.