They utterly destroyed them That is, as many of them as they took at that time; but it is plain that all these Canaanites were not destroyed at this time, for we find the king of Arad and the king of Hormah mentioned among the kings whom Joshua smote some time after this, Joshua 12:14; and several of their cities were not taken and destroyed till after the death of Joshua, Judges 1:16-17. Indeed, all that the Hebrew here (יחרם, jacharem) signifies is, that they now devoted them and their cities to destruction, and when their cities came into their possession they fulfilled their vow. He called the name of the place Hormah That is, devoted to destruction, or, Anathema.
Related Commentaries of Numbers 21:3
Numbers 21:3
3 And the LORD hearkened to the voice of Israel, and delivered up the Canaanites; and they utterly destroyed them and their cities: and he called the name of the place Hormah.a