An important aspect to understand soteriological implications is that “faith” is not the “act of acceptance” like circumcision was to the Covenants. Meaning, an act of acceptance is a “one-time” act that works as a witness or testimony to others that we accepted the free, unilateral gift of salvation. Circumcision was that one-time “act of acceptance” for both the Abrahamic and Mosaic Covenant. As believers, many look for our circumcision, but our circumcision is the putting off of the flesh and getting a new heart. Jer. 4 speaks about Israel as not circumcising their hearts. Matter of fact, Heb. 3-4 is all about the Mosaic Covenant and the importance of “faith” that accompanied their works (because of their unbelieving heart they did not enter into the promise land). The promise was to Abraham and his Seed (Christ). The Mosaic Covenant was a whole different covenant Gal. 3:17 “And this I say, that the law, which was four hundred and thirty years later, cannot annul the covenant that was confirmed before by God in Christ, that it should make the promise of no effect.” Which, I am sure, you already know.
But, what about “eternal salvation”? Can we “lose” our faith. The answer is easy. It cannot be taken from us, but since the ongoing condition of our salvation is faith, we must continue in faith to enter into our promise land. The entire book of Hebrews is dedicated to explaining our enduring faith. That is why Paul said, “holding on to faith and a good conscience, which some have rejected and so have suffered shipwreck with regard to the faith” 1 Tim. 1:19. So, faith is the substance of our salvation and not the act. But, how do we lose our faith. Heb. 3 tells us that sin “hardens the heart.” Our sin can harden our heart and have us doubt our faith so that we will be as blind leading the blind. Our most precious faith. That is why we are told to guard it, “Be on your guard; stand firm in the faith; be courageous; be strong.”
By faith we are saved and our act of acceptance is not only the circumcision of the heart, but the confession of the lips that “Jesus is Lord.”
On a side note, baptism is not necessarily portrayed as the “act of acceptance” but it is clear that is it necessary for salvation. Since an “act of acceptance” is a one-time act, and to have both confession that Jesus is Lord with the lips AND baptism forces me to thing baptism may be its own, separate entity. This is why I say that. When you see our “salvation” mentioned, you will see “faith” and “confession that Jesus is Lord” time and time again. Baptism is not immediately or always mentioned together with these two. Therefore, I go to the Old Testament. When trying to connect baptism as a need for salvation in the Old Testament we are taken a few places. First, it is closely reflected in the Mikvah and Moses/people baptized in the red-sea and the cloud. We also see this previously implied with Elijah and Elisha. And finally, John the Baptist (still under the Law) and those who came confessing/repenting in the Jordan. They were baptized so their eyes could be open to recognize the Christ. It is important to note that the women (for the first time in her life) will be mikvah’d right after she gets betrothed to be married. This worked as a purifier and cleansing unit as the Church was washed with the water of the word. His bride.
I look at baptism/faith/confession of the Lord as I look to God, Jesus and the Holy Spirit (trinity). The close relationship between God the Father and Jesus, His son is often mentioned together. It will mention the Holy Spirit either by itself or with Jesus later. We see a family relationship with the Father and Son right off the bat, even though we understand these three (Father/Son/Holy Spirit) seem to be critically intertwined in the Heavenly. Therefore, I look at the Abrahamic and Mosaic Covenant and see how baptism or mikvah was essential for their covenant and salvation. I don’t see it mentioned as clear as it is with ours, so it makes me wonder if baptism is that first symbolic “work” or “duty” that is needed to be performed. Since baptism is a one-time shot, I see it more as symbolic event rather than a work like those in the Mosaic Covenant.