Just a quote from Fred A. Malone quoting John Owen.
When we speak of the "new Covenant" we do not intend the covenant of grace absolutely, as though that were not before in this place. For it was always the same, as to the substance of it, from the beginning. It passed through the whole dispensation of times before the law, and under the law, of the same nature and efficacy, unalterable, "everlasting, ordered in all things, and sure." All who contend about these things, the Socianians only excepted, do grant that the covenant of grace, considered absolutely,- that is, the promise of grace in and by Jesus Christ, - was the only way and means of salvation unto the church, from the first entrance of sin. But for two reasons it is not expressly called a covenant, without respect unto any other things, nor was it so under the old testament. When God renewed the promise of it unto Abraham, he is said to make a covenant with him; and he did so, but was with respect unto other things, especially the proceeding of the promised Seed from his loins. But absolutely under the Old testament it consisted only in a promise; and as such only is proposed in the Scriptures, Acts 2:39; Jer 6:14-16. The apostle indeed says, that the covenant was confirmed of God in Christ, before the giving of the law, Gal 3:17. And so it was, not absolutely in itself, but in the promise and benefits of it. The nomothesia, or full legal establishment of it, whence it became formally a covenant unto the whole church, was future only, and a promise under the old testament... but now, under the new testament, this covenant, with its own seals and appointments, is the only rule and measure of all acceptable worship. Wherefore the new covenant promised in the Scripture, and here opposed unto the old, is not the promise of grace, mercy, life and salvation by Christ, absolutely considered but as it had the formal nature of a covenant given unto it, in its establishment of the death of Christ, the procuring cause of all its benefits, and the declaring of it to be the only rule of worship and obedience unto the Church. So that although by the covenant of grace," we oftentimes understand not more but the way of life, grace, mercy, and salvation by Christ yet by "the new covenant" we intend its actual establisment in the death of Christ with that blessed way of worship whcih by it is settle in the church.
John Owen quoted Hebrews 6: 74-75
...The promise of the New Covenant, the purer administration of the Covenant of Grace, was part of the Abrahamic Covenant. However the Abrahamic Covenant also contained other elements regarding Abraham's seed that were unique to its administration until the final "Seed" comes (Galatians 3:16,19). ... Each covenant's content must be determined by specific revelation concerning that covenant.
quotes taken from
The Baptism of Disciples Alone
Fred Malone
pp 61,62
