Did the OT saints obey God, or did they try?
You see, they are in the same situation - Justified by FAITH. Not by LAW.
The LAW was only to show you cannot be justified by works.
But they had faith in the coming redeemer, the messiah, God with us!
They knew His titles, but not His name.
So all were and are saved by the same agency - Belief in Jesus.
(Either knowing His name (as we Christians are privileged to) or not).
Are you familiar with the story of the Prodigal Son?
The Gentiles are the younger brother, we ate with the pigs and left the things of God after the fall.
The Jews are the older brother, who stayed in the field.
Note that the older brother would NOT come into the feast when the younger brother returned.
Likewise, the Gentiles have returned to God, but the Jews stay in the field, not attending the celebration.
The parable ends with that issue hanging out. The older brother is still in the field.
But we know from prophecy the older brother WILL return and celebrate with the Father.
WE (the younger brother) should write the older brother out of the family. That decision is the Fathers, not ours.
We are all the prodigal son when we sin. We are all the older brother when we resent seeing a sinner forgiven.
The prodigal son in the story was Jewish. He worked with pigs to emphasize his degradation; how far he had fallen.