Calvin's Commentaries, Vol. 3: Harmony of the Law, Part I, tr. by John King, [1847-50], at sacred-texts.com
Deut. 4:1, 2
1. Now therefore hearken, O Israel, unto the statutes, and unto the judgments, which I teach you, for to do them, that ye may live, and go in and possess the land which the Lord God of your fathers giveth you.
1. Et nunc Israel audi statuta et judicia, quae ego doceo vos, ut faciatis: ut vivatis, atque ingrediamini, et possideatis terram quam Jehova Deus patrum vestrorum dat vobis.
2. Ye shall not add unto the word which I command you, neither shall ye diminish ought from it, that ye may keep the commandments of the Lord your God which I command you.
2. Non addetis ad verbum quod ego praecipio vobis, neque minuetis ex eo, ut custodiatis praecepta Jehovae Dei vestri, quae ego praecipio vobis.
1. Now, therefore, hearken, O Israel. He requires the people to be teachable, in order that they may learn to serve God; for the beginning of a good and upright life is to know what is pleasing to God. From hence, then, does Moses commence commanding them to be attentive in seeking direction from the Law; and then admonishing them to prove by their whole life that they have duly profited in the Law. The promise which is here inserted, only invites them to unreserved obedience through hope of the inheritance. The main point is, that they should neither add to nor diminish from the pure doctrine of the Law; and this cannot be the case, unless men first renounce their own private feelings, and then shut their ears against all the imaginations of others. For none are to be accounted (true) disciples of the Law, but those who obtain their wisdom from it alone. It is, then, as if God commanded them to be content with His precepts; because in no other way would they keep His law, except by giving themselves wholly to its teaching. Hence it follows, that they only obey God who depend on His authority alone; and that they only pay the Law its rightful honor, who receive nothing which is opposed to its natural meaning. The passage is a remarkable one, openly condemning whatsoever man’s ingenuity may invent for the service of God.