Hebrews 2:2 For if the word spoken by angels was stedfast, and every transgression and disobedience received a just recompence of reward;
A just recompense of reward. God is just. God is righteous. All that He does is right. He will deal with the sin of the world in a just and right way. Hebrews 2:2 tells us this. Every transgression and every disobedience will receive a just recompense of reward. Recompense refers to compensation. The author here is telling us that for every transgression and disobedience a just or fair compensation will be given. We have seen the wages of sin is death. This wage, this compensation will be just as it is handed down from a just God. How could any in the Old Testament hope to escape this just recompense? It would be by the forbearance of God.
God would patiently tolerate the sins of all those from the Old Testament until that time that He had purposed to deal with their sins. Just as our sin was dealt with before we were alive, their sin was dealt with long after some of them had gone. In either way justice prevailed and God remained holy and righteous. This declared His righteousness in delaying punishment of their sin as not one sin went unpunished. God was forbearing with all the sins of all His people waiting for that propitiation to come. He could have cast all of humanity into hell as everyone of us deserve a just recompense for each and every transgression and disobedient action we have committed. God would be patient, forbearing on our accounts until His Son would give His life, shed His blood which was given for the remission of sins.
One more verse to illustrate.
2 Peter 3:15 And account that the longsuffering of our Lord is salvation; even as our beloved brother Paul also according to the wisdom given unto him hath written unto you;
Here Peter takes some of the writing of Paul to show how the longsuffering of God is our salvation. Could God have condemned all Adam’s seed to eternal condemnation and sent them to eternal punishment then and there and remained just in doing so? The answer is yes, He could have done just that. What God chose to do was to forbear with the sin of even His elect people waiting for that time the propitiation would come.