6 If your very own brother, or your son or daughter, or the wife you love, or your closest friend secretly entices you, saying, "Let us go and worship other gods" (gods that neither you nor your ancestors have known, 7 gods of the peoples around you, whether near or far, from one end of the land to the other), 8 do not yield to them or listen to them. Show them no pity. Do not spare them or shield them. 9 You must certainly put them to death. Your hand must be the first in putting them to death, and then the hands of all the people. 10 Stone them to death, because they tried to turn you away from the Lord your God, who brought you out of Egypt, out of the land of slavery.

Matthew Henry's Commentary on Deuteronomy 13:6-10

Commentary on Deuteronomy 13:6-11

(Read Deuteronomy 13:6-11)

It is the policy of Satan to try to lead us to evil by those whom we love, whom we least suspect of any ill design, and whom we are desirous to please, and apt to conform to. The enticement here is supposed to come from a brother or child, who are near by nature; from a wife or friend, who are near by choice, and are to us as our souls. But it is our duty to prefer God and religion, before the nearest and dearest friends we have in the world. We must not, to please our friends, break God's law. Thou shalt not consent to him, nor go with him, not for company, or curiosity, not to gain his affections. It is a general rule, If sinners entice thee, consent thou not, Proverbs 1:10. And we must not hinder the course of God's justice.

20 But a prophet who presumes to speak in my name anything I have not commanded, or a prophet who speaks in the name of other gods, is to be put to death."

Matthew Henry's Commentary on Deuteronomy 18:20

Commentary on Deuteronomy 18:15-22

(Read Deuteronomy 18:15-22)

It is here promised concerning Christ, that there should come a Prophet, great above all the prophets; by whom God would make known himself and his will to the children of men, more fully and clearly than he had ever done before. He is the Light of the world, John 12:48. Woe then to those who refuse to hearken to His voice, to accept His salvation, or yield obedience to His sway! But happy they who trust in Him, and obey Him. He will lead them in the paths of safety and peace, until He brings them to the land of perfect light, purity, and happiness. Here is a caution against false prophets. It highly concerns us to have a right touchstone wherewith to try the word we hear, that we may know what that word is which the Lord has not spoken. Whatever is against the plain sense of the written word, or which gives countenance or encouragement to sin, we may be sure is not that which the Lord has spoken.