Concerning the Covenants [De Foederibus]
The old covenant or testament was established in accordance with the righteousness of God through the Law, so that the righteousness of God might be vindicated from the false accusations of men; so that men would be inexcusable, guilty, and convicted by the old covenant and not absolved by their merits. Further, in order that the old covenant, with its own law, ceremonies, and shadows should be a witness of the new; and to some extent a sacrament of the new covenant (as it is written in Heb. 8, 10).
That covenant is transitory. Nevertheless, on God’s part, it has the bond of stipulation from a superior party. On the part of the inferior party, in temporal shadows, it is based on the strength of men. Therefore, it becomes invalid because of feeble men (Jer. 31; Isa. 59). In the old covenant, there is no equal proportion between the infinite, righteous God who commands and unrighteous, finite, mortal man who carries out the commands; for that reason, it becomes void.
The new covenant is called an eternal testament, consecrated by the grace and mercy of God in the blood of the eternal sacrifice of Christ, with all its causes founded on Christ. In this covenant, the grace of God and the merit of Christ are placed in the stipulations on both parts (Gal. 3; Zech. 9). The things which God demands, He promises to the doer and accomplishes Himself. It is God that demands and that promises; in Christ, He is also the one under obligation.
For in every stipulation, there are these two things. First, on the part of the superior stipulator, both the one who makes demands and promises to perform the demands; on the part of the inferior, the doer and the one obligated (Matt. 26; Luke 22). In the new covenant, God is the stipulator, but Christ is the performer undertaking the obligation in our name. The sacraments, i.e., baptism and the Lord’s Supper, are the seals of these stipulations of God and Christ.
This covenant will remain forever because its two main points (its foundation and terminus) are in God. It is tied to the grace of God and Christ; there is equity or equal harmony; there is a proportion between Him that commands and promises and Jesus who accomplishes. He that accomplishes is like Him that promises (Heb. 10; Jer. 31).
“The Hungarian Confessio Catholica (1562),” in James T. Dennison Jr., Reformed Confessions of the 16th and 17th Centuries in English Translation: 1523–1693, 4 vols. (Grand Rapids, MI: Reformation Heritage Books, 2008–2014), 2:474–475. Primary source (via PRDL)