The covenant of God generally is a promise under some one certain condition. And it is twofold; the first is the covenant of works; the second is the covenant of grace. Paul ( Gal. iv. 24) expressly sets down two covenants, which in the Old Testament were shadowed by two women, as by types, to wit, Hagar, the handmaid, and Sarah, the free woman; for, saith he, these be those two covenants. Let us then speak something of these two covenants; and first of the covenant of works. The covenant of works, which may also be called a legal or natural covenant, is founded in nature, which by creation was pure and holy, and in the law of God, which in the first creation was engraven in man’s heart. For after that God had created man after his own image, pure and holy, and had written his law in his mind, he made a covenant with man, wherein he promised him eternal life, under the condition of holy and good works, which should be answerable to the holiness and goodness of their creation, and conformable to his law. And that nature thus beautified with holiness and righteousness and the light of God’s law, is the foundation of the covenant of works, it is very evident; for that it could not well stand with the justice of God to make a covenant under condition of good works and perfect obedience to his law, except he had first created man pure and holy, and had engraven his law in his heart, whence those good works might proceed. For this cause, when he was to repeat that covenant of works to the people of Israel, he first gave the law written in tables of stone; then he made a covenant with his people, saying, Do these things, and ye shall live. Therefore the ground of the covenant of works was not Christ, nor the grace of God in Christ, but the nature of man in the first creation holy and perfect, endued also with the knowledge of the law. For, as touching the covenant of works, there was no mediator in the beginning between God and man, that God should in him, as in and by a mediator, make his covenant with man. And the cause that there was no need of a mediator was this, that albeit there were two parties entering into a covenant, yet there was no such breach or variance betwixt them that they had need of any mediator to make reconciliation between them; for, as for the covenant of works, God made this covenant with man, as one friend doth with another. For in the creation we were God’s friends, and not his enemies. Thus far of the ground of the covenant of works.
—Robert Rollock, A Treatise Of God’s Effectual Calling (1597), trans. 1849, 34–35.