The Lord had said, "Thou shalt have none other gods but Me." A prophet is here supposed who invites the people "to go after other gods." To such a one no credit is under any circumstances to be given, even should he show signs and wonders to authenticate his doctrine. The standing rule of faith and practice had been laid down once for all - that the people were to hold fast. The prophet who propounded another rule could only be an impostor.

A different case is considered in Deuteronomy 18:18, etc.

And the sign and wonder come to pass whereof he spake unto thee,.... The sign he promised to give, or the miracle he proposed to do, to show the reality of his mission, and the truth of his doctrine, which is performed, or seemingly performed, by legerdemain, by magic art, or by the help of the devil; which the Lord sometimes suffered for the trial of the faith and obedience of his people, and for the hardening of others in their unbelief, and which issues in their destruction; see 2 Thessalonians 2:9,

saying, let us go after other gods (which thou hast not known), and let us serve them; other gods besides the one living and true God, the Creator of all things; strange gods, the idols of the people, as the Targum of Jonathan; such as they had never heard of, nor had any knowledge of, nor any benefit from, as they had of the Lord their God. Now the doctrines of these, and of their worship, are what the false prophet or dreamer is supposed to come with, and inculcate into the minds of the people; and for the confirmation of which, and in order to draw them into the reception of them, and act according to them, he proposed to give a sign or wonder.

And the sign or the wonder come to pass, whereof he spake unto thee, saying, {b} Let us go after other gods, which thou hast not known, and let us serve them;

(b) He shows that to which the false prophets tend.

13:1-5 Moses had cautioned against the peril that might arise from the Canaanites. Here he cautions against the rise of idolatry among themselves. It is needful for us to be well acquainted with the truths and precepts of the Bible; for we may expect to be proved by temptations of evil under the appearance of good, of error in the guise of truth; nor can any thing rightly oppose such temptations, but the plain, express testimony of God's word to the contrary. And it would be a proof of sincere affection for God, that, notwithstanding specious pretences, they should not be wrought upon the forsake God, and follow other gods to serve them.