Saving Faith that Gives us the Righteousness of God, for Eternal Life, did not began in the New Testament but was and is available for all who believe. Romans 4 is very clear that the Salvation we have, Abraham, our "father of faith" also had and received it in the same way we do today. In this chapter Apostle Paul clearly details how God's Righteousness was imputed to Abraham by Faith Alone, without works. In this he notes it was granted because "Abraham believed God, and it was counted unto him for righteousness." (Romans 4:3 and Genesis 15:6). He then goes into detail explaining that it was before circumcision or any covenant, Law, or work. He then ends the passage with showing us that Abrahams faith for Righteousness is the same as our faith, without difference and was given to us as the example to follow.
In this message we touch on the error of "dispensational salvation" which attempts to divide up the manner of salvation (typically trying to include works, nationality, or covenant as a requirement) depending on when they live or what knowledge they had and the focus of salvation (faith merely in the physical act in time). We note just as death and condemnation of sin is the same, so too is the manner of salvation, by Believing on Christ for God's Righteousness (John 8:56 Your father Abraham rejoiced to see my day: and he saw it, and was glad.). We show how God's Promise to Abraham to be a father of many nations and to give him a son was about Saving Faith and the Coming of Christ to give that salvation, Isaac being an "Earnest payment" of that future promise of Saving Faith. We show it is unto all and upon all who believe in Christ (and not necessarily only on those who had full knowledge of certain events within time). In other words it is granted by faith in God's promise of salvation and Christ's ability to save us and not based on our knowledge of or faith in events that occurred within time ("God, who quickeneth the dead, and calleth those things which be not as though they were.").
(Preached Sunday morning, 11-28-2021, by Pastor John Young, at Maranatha Bible Baptist Church, 16990 S 38th St, Mendon, MI 49072, Between Fulton and Menden in Wakeshma Township, Near Kalamazoo and Battle Creek in South West Michigan, https://www.facebook.com/MbbcFulton)