3. BASICALLY, THE COVENANT OF GRACE IS SIMPLY THE EXECUTION OF THE ORIGINAL AGREEMENT BY CHRIST AS OUR SURETY. He undertook freely to carry out the will of God. He placed Himself under the law, that He might redeem them that were under the law, and were no more in a position to obtain life by their own fulfilment of the law. He came to do what Adam failed to do, and did it in virtue of a covenant agreement. And if this is so, and the covenant of grace is, as far as Christ is concerned, simply the carrying out of the original agreement, it follows that the latter must also have been of the nature of a covenant. And since Christ met the condition of the covenant of works, man can now reap the fruit of the original agreement by faith in Jesus Christ.
—Louis Berkhof, Systematic Theology (Grand Rapids, MI: Wm. B. Eerdmans publishing co., 1938), 214.