Calvin's Commentaries, Vol. 4: Harmony of the Law, Part II, tr. by John King, [1847-50], at sacred-texts.com
Deut. 11:16, 17
16. Take heed to yourselves, that your heart be not deceived, and ye turn aside, and serve other gods, and worship them;
16. Cavete ergo vobis ne seducatur cor vestrum, et recedatis, colatisque deos alienos, et vos incurvetis coram eis.
17. And then the LORD’S wrath be kindled against you, and he shut up the heaven, that there be no rain, and that the land yield not her fruit; and lest ye perish quickly from off the good land which the LORD giveth you.
17. Unde excandescat ira Jehovae in vos, et claudat coelos ne sit pluvia, ac ne det terra fructum suum: pere-atisque celeriter e terra bona quam Jehova dat vobis.
16 Take heed to yourselves. By often inculcating the same thing, viz., that they should diligently take heed, he indirectly arraigns man’s proneness to superstition; and this too is again expressed in the words, “that your heart be not deceived;” for by them he signifies, that unless they take diligent heed to themselves, nothing will be more easy than for them to fall into the snares of Satan. Wherefore the impudence of the Papists is the less excusable, who intoxicate their own and others’ minds with security, when God constantly exhorts them to solicitude. Let us learn, then, that since many impostures and deceits besiege us on every side, we shall in the vanity of our nature be liable immediately to fall into them, unless we carefully guard ourselves. By the expression “turn aside,” he implies what has been before said, that whosoever declines to corrupted worship, impiously falls away from the true God. Unbelievers but little think so, for with them it is a light transgression to exceed in this respect; and they would wilfully blind the eyes of God with their inventions (commentis), nay, there is nothing too silly for them to desire to be approved of, and sanctioned by God. But if it be objected that obedience is better than sacrifice, they shield themselves under the cover of their good intention, as if God were not at liberty to repudiate what they foolishly obtrude upon Him. At any rate, they so pertinaciously indulge themselves in their inconsiderate zeal, that they will hardly acknowledge the slightest fault in it. But, on the other side, God declares that all are apostates who do not confine themselves to the simplicity of the Law. A threat is again added, that God will avenge the violation of His worship, and will curse their land, until He shall destroy them by dearth and famine; and, finally, He pronounces that they shall perish off that land which God had promised them to the end that He might be there purely worshipped.