21:1-3 Before the people began their march round the country of Edom, the king of Arad, a Canaanite, who inhabited the southern part of the country, attacked them in the wilderness, and took some prisoners. This was to lead the Israelites to look more thoroughly to the Lord.
2, 3. Israel vowed a vow unto the Lord—Made to feel their own weakness, they implored the aid of Heaven, and, in anticipation of it, devoted the cities of this king to future destruction. The nature and consequence of such anathemas are described (Le 27:1-34; De 13:1-18). This vow of extermination against Arad [Nu 21:2] gave name to the place Hormah (slaughter and destruction) though it was not accomplished till after the passage of the Jordan. Others think Hormah the name of a town mentioned (Jos 12:14).