The word testamentum is often used in Latin to express the Hebrew word which signifies covenant; whence the titles, Old and New Testaments, are used to denote the old and new covenants. See TESTAMENT.
A covenant is properly an agreement between two parties. Where one of the parties is infinitely superior to the other, as in a covenant between God and man, there Godís covenant assumes the nature of a promise, Isaiah 59:21 Jeremiah 31:33,34 Galatians 3:15-18. The first covenant with the Hebrews was made when the Lord chose Abraham and his posterity for his people; a second covenant, or a solemn renewal of the former, was made at Sinai, comprehending all who observe the law of Moses. The "new covenant" of which Christ is the Mediator and Author, and which was confirmed by his blood, comprehends all who believe in him and are born again, Galatians 4:24 Hebrews 7:22 8:6-13 9:15-23 12:24. The divine covenants were ratified by the sacrifice of a victim, to show that without an atonement there could be no communication of blessing and salvation form God to man, Genesis 15:1-8 Exodus 24:6-8 Hebrews 9:6. Eminent believers among the covenant people of God were favored by the establishment of particular covenants, in which he promised them certain temporal favors; but these were only renewals to individuals of the "everlasting covenant," with temporal types and pledges of its fulfilment. Thus God covenanted with Noah, Abraham, and David, Genesis 9:8,9 17:4,5 Psalms 89:3,4, and gave them faith in the Savior afterwards to be revealed, Romans 3:25 Hebrews 9:15.
In common discourse, we usually say the old and new testaments, or covenants-the covenant between God and the posterity of Abraham, and that which he has made with believers by Jesus Christ; because these two covenants contain eminently all the rest, which are consequences, branches, or explanations of them. The most solemn and perfect of the covenants of God with men is that made through the mediation of our Redeemer, which must subsist to the end of time. The Son of God is the guarantee of it; it is confirmed with his blood; the end and object of it is eternal life, and its constitution and laws are more exalted than those of the former covenant.
Theologians use the phrase "covenant of works" to denote the constitution established by God with man before the fall, the promise of which was eternal life on condition of obedience, Hosea 6:7 Romans 3:27 Galatians 2:19. They also use the phrase, "covenant of grace or redemption," to denote the arrangement made in the counsels of eternity, in virtue of which the Father forgives and saves sinful men redeemed by the death of the Son.
These dictionary topics are from American Tract Society Bible Dictionary published in 1859. Public Domain, copy freely.