3. In the promises. The law promises life to those who are righteous in themselves, or on the condition of righteousness, and perfect obedience. “He that doeth them, shall live in them.” “If thou wilt enter into life, keep the commandments.” (Lev. 18:5. Matt. 19:17.) The gospel, on the other hand, promises life to those who are justified by faith in Christ, or on the condition of the righteousness of Christ, applied unto us by faith. The law and gospel are, however, not opposed to each other in these respects: for although the law requires us to keep the commandments if we would enter into life, yet it does not exclude us from life if another perform these things for us. It does indeed propose a way of satisfaction, which is through ourselves, but it does not forbid the other, as has been shown.
—Zacharias Ursinus, The Commentary of Dr. Zacharias Ursinus on the Heidelberg Catechism, trans. G. W. Williard (Cincinnati, OH: Elm Street Printing Company, 1888), 104–05.