In that he says, A new covenant, he has made the first old.     Now that which decays and waxes old is ready to vanish away. - Heb 8:13 Paul preached the Gospel of Grace Through Faith which stands completely on its own with no dependence on prior covenants or standards for righteousness.      However, some believers then and now still hang on to performance aspects of the law as requirements for Spirit Salvation.     This is error.      Forgiveness of sins is a done deal Heb 8:12.      Eternal Life in the New Birth comes by faith in Christ Jesus Rom 6:23.      We then walk by faith in the Word so that we experience Abundant Life Joh 7:38.      Salvation is two-part: Spirit Salvation and Soul Salvation.

The Gospel is nearly too good to be true news.   It is because its 'unbelievability' that many believers revert to some measure of legalism in order to feel justified.   

The Old Covenant meets that need to be justified by contributing to our salvation.   

But such turning back to that which never brought salvation to anyone Jam 2:10 and away from the finished work Joh 17:4 of Christ Jesus is a major insult to our Lord.   

Of how much severer punishment, suppose you, shall he be thought worthy, who has trodden under foot the Son of the Holy Spirit, and has counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and has done despite unto the Spirit of grace? - Heb 10:29 This verse applies to all who reject the Gospel of Jesus Christ.

But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed. - Gal 1:8 Paul curses those who preach a perverted gospel because they are doing the work of Satan.

The pure Gospel is that we are Accepted In The Beloved by Grace Through Faith In Christ Jesus.   

Any stance that is taken other than Grace denies the efficacy of the BloodOfChrist leaving such in condemning unbelief.   

There is no such thing as an Old Testament Christian so don't allow Satan to condemn you into going back to that which never worked.   

For the wages of sin is death; but the gift of the Lord is eternal life through Jesus Christ our Lord. - Rom 6:23 The sin that condemns to the Lake Of Fire is rejection of Jesus Christ Joh 3:18.      The gift of the Lord Jesus is His own Eternal Life, which is relationship with His Holy Spirit Joh 5:26.      There are two types of death: → physical death Heb 9:27 → spiritual death Rev 21:8.      Adam and Eve did not immediately die physically when they sinned.     However, they immediately died spiritually Gen 2:17.      When a person sins, whether believer or unbeliever, the result is an aspect of death.     Somethings shrinks or shrivels instead of growing when sin occurs Joh 10:10.      Jesus gives us His life - Eternal Life when we believe on Him.     That gift is irrevokable Joh 14:16.      However, if we let sin reign in our mortal bodies we will suffer the consequences of that sin destroying our physical lives, our testimonies and our walk with the Lord Col 1:10.      Instead of us living a victorious, productive life with treasure laid up in heaven, we will be saved as by fire 1Cor 5:5.

For by grace are you saved through faith; and that not of yourselves: it is the gift of the Lord: - Eph 2:8 We are saved because the Lord willed it Heb 8:12 and made it possible and legal through the shed blood of Jesus Christ Heb 10:10.      salvation is totally an act of the Lord's unmerited favor - Grace.     Our part is to have faith in His Word - the Written Word and the Incarnate Word Act 16:31.      We have all been given The Measure Of Faith Rom 12:3.      It is that gift of faith than enables us to believe on the Lord Jesus Christ through whom we receive Grace 2Pe 1:3.      Once we believe on the Lord Jesus Christ, the Faith Of Christ provides all the benefits of Grace Rom 5:2.      The Faith Of Christ is the foundation of Grace Rom 5:19.      We are not supposed to trust in our faith but, rather, trust in the Faith Of Christ Phi 2:8-11.

It is important for us to grasp the fact that Jesus is the Truth about our Creator because He is our Creator and He is the one who has the power to receive us or reject us.