Commentary for Numbers 31:8

חמשת מלכי מדין THE FIVE KINGS OF MIDIAN — But can I not see that Scripture has enumerated five; why, then, does it feel compelled to say that there were five? But it is to tell you that even as they had all been alike in the plot, so, too, they were treated alike in the punishment that befell them (cf. Rashi on Genesis 25:22, where, as here, the total of the names mentioned is stated) (Sifrei Bamidbar 157:5). — Balaam had gone there to receive the reward for the 24,000 whom he had made to fall of Israel through his counsel and now also he left Midian to meet Israel and gave them bad advice: viz., he said to them, “If, when you were 600,000 you were unable to overcome them, now you come to war against them with 12,000?” They gave him his full reward and did not stint it (they slew him) (Sifrei Bamidbar 157:5).

ואת מלכי..חמשת מלכי מדין, "and the kings of Midian….-the five kings of Midian." The reason that the Torah spelled out their number (i.e. 5), something we had already counted ourselves, was to tell us that they were all killed next to one another so that all the soldiers could count the bodies of these five kings whom they had slain. The reason why the Torah repeats that they were kings may have been to tell us that they were killed by soldiers who knew full well that these five men were kings. They were not the victims of random killings.

ואת צור, “and Tzur;” the father of Cozbi חמשת מלכי מדין, “the five kings of Midian.” The reason the Torah wrote the word חמשת מלכי מדין as if mentioning their names did not already tell us that there five such kings, is to tell us that all five were of one mind concerning their hostility against Israel. The construct form חמשת reflected this. The reason that Bileam was there was that he had detoured on his way home, (a long way off from Aram) in order to collect his reward for having been the cause of the 24,000 men of Shimon killed by the plague, Bileam had mocked the Israelites saying: “if you could not go to war against Midian when there were 600,000 of you, how can you now expect to defeat them with only 12,000 men?” He had tried to undermine their self-confidence (compare Tanchuma Mattot 3). [The challenge by Bileam reported here is not found in Tanchuma. Ed.]