The early Zurich theology preached a postlapsarian covenant of grace (i.e. established after the fall of man) which is bilateral, contemplating a mutual pact between God and humanity, with conditions that God makes certain promises and humanity undertakes certain duties of obedience. It is a single covenant, binding together all of God’s covenantal transactions (or “leagues”) with Adam, Noah, Abraham, and Moses in the Old Testament, which are seen as anticipations of the new covenant in Jesus Christ. The unity of the covenant flows from the unity of God’s ways with humanity. In the passage below, Heinrich Bullinger (1504-1575) explains the covenant idea in a sermon on the law:
“When God’s mind was to declare the favour and good-will that he bare to mankind, and to make us men partakers wholly of himself and his goodness, by pouring himself out upon us, to our great good and profit, it pleased him to make a league or covenant with mankind. Now he did not first begin the league with Abraham, but did renew to him the covenant that he had made a great while before. Now he did first of all make it with Adam, the first father of us all, immediately upon his transgression, when he him, silly wretch [iam profugum, ‘now become an outcast’], into his favour again, and promised his only-begotten Son, in whom he would be reconciled to the world, and through whom he would wholly bestow himself upon us, by making us partakers of all his good and heavenly blessings, and by binding himself in faith and due obedience. This ancient league, made first with Adam, he did afterward renew to Noah, and after that again with the blessed patriarch Abraham. And again, after the space of four hundred years, it was renewed under Moses at the mount Sinai, where the conditions of the league were at large written in the two tables, and many ceremonies added thereunto. But most excellently of all, most clearly and evidently, did our Lord and Saviour Jesus Christ himself shew forth that league; who wiping away all the ceremonies, types, figures and shadows, brought in instead of them the very truth, and did most absolutely fulfil and finish the old league, bringing all the principles of our salvation and true godliness into a brief summary, which, for the renewing and fulfilling of all things, and for the abrogation of the old ceremonies, he called the new league or testament…
But now I return to the league which was renewed with Abraham. We are expressly taught in Genesis, who they were that made the league; that is, the living, eternal, and omnipotent God, who is the chief maker, preserver, and governor of all things; and Abraham with all his seed, that is, with all the faithful, of what nation or country soever they be. For so doth the Apostle expound the seed of Abraham, especially in his epistle to the Galatians, where he saith, ‘If ye be Christ’s, then are ye the seed of Abraham, and heirs by promise’ [Gal. iii. 29].
The time, how long this league should endure, is eternal, and without end or term of time. For although, in the renewings or declarations of the league, many things were added which afterward did vanish away, especially when Christ was come in the flesh; yet notwithstanding, in the substantial and chiefest points, ye can find nothing altered or changed. For God is always the God of his people: he doth always demand and require of them faithful obedience; as may most evidently be perceived in the New Testament.
For there are two points, or especial conditions, contained in this league: the first whereof declareth what God doth promise, and what he will do for his confederates; I mean, what we may look for at his hands: the second comprehendeth the duty of man, which he doth owe to God, his confederate and sovereign prince.”
– Heinrich Bullinger (1504-1575), “Of the Ceremonial Laws of God”, Decades, 2:169-175