This is where I start having some issue with dispensationalist opinion. I think grace has always been, always will be the salvation. I believe we have it easy in a sense but Grace always in my view. I`m also pre wrath in my view of the first resurrection.
It is always by God's grace for ALL dispensations, don't get me wrong.
Our response to that grace, is by faith. And how we respond by faith differs depending on which dispensation we are in.
During the dispensation of the law, you exhibit faith by "obeying the law", all the Jews have to obey the law. It is true that all the saints of past ages were saved through the merits of Christ's shed blood, but not through their faith in that shed blood.
Those of past ages were expected to believe only what God had thus far revealed, or what He had revealed to them. In other words, they were saved simply because they trusted God and believed what He said. The full plan of salvation has since been unfolded, but the Scriptures make it crystal clear that these believers were saved without even understanding that Christ would die for them.
When God says, "Repent and be baptized for the remission. of sins," what will faith do? Just one thing: repent and be baptized. We know that oceans of water cannot wash away one sin, yet when John the Baptist and Peter preached repentance and baptism for remission not one of their hearers would have interpreted their words to mean: "Trust in the death of Christ for salvation."
Indeed, when God required water baptism for salvation the only way to manifest faith was to be baptized, and those who refused to do so were condemned for their unbelief:
"But the Pharisees and lawyers REJECTED THE COUNSEL OF GOD
AGAINST THEMSELVES, BEING NOT BAPTIZIED OF HIM" (Luke 7:30).
But when God says, "BUT NOW the righteousness of God without the law is manifested" (Rom. 3:21); "To him that worketh not, but believeth on Him that justifieth the ungodly, his faith is counted for righteousness" (Rom. 4:5); "Being Justified freely by His grace, through the redemption that is in Christ Jesus" (Rom. 3:24); "In whom we have redemption through His blood, the forgiveness of sins according to the riches of His grace" (Eph. 1:7); "Not by works of righteousness which we have done, but according to His mercy He saved us" (Tit. 3:5); "Not of yourselves: it is the gift of God: not of works, lest any man should boast" (Eph. 2:8,9) -
When God now says this, what will faith do? Faith will say, "This is the most wonderful offer ever made by God to man. I cannot refuse it. I will trust Christ as my Savior and accept salvation as the free gift of God's grace."