Regarding the tribe of Levi, Maimonides explains that "they were separated from worldly affairs [and therefore] did not fight in the wars like the rest of the people of Israel." The Levites were chosen to dedicate themselves to the work in the Temple and to sanctify themselves completely for the service of God; therefore, they did not join the rest of the people in the successive wars of conquest of the Land. However, there was one war in which the sons of Levi also participated: the war against Midian, which is discussed in this week's section. Regarding this war, Moses said, "To all the tribes of Israel, send the army," and from this our sages learned that the word all ""It includes the tribe of Levi." What is so special about this war that even the Levites were sent to fight in it?
The war against Midian was unlike any other war. Its objective was not the conquest of land, but rather to exact God's vengeance on Midian. The Midianites had defied God and led the Jewish people into sin, so the war against them served to destroy God's enemies. For this type of war, the tribe of Levi was also commanded to join the rest of the people, as this is part of the function of God's army—to complete God's vengeance."
Therefore, the sons of Levi also received a special share of the spoils of war. This expresses the special nature of this war, unlike the others (in which the Levites did not receive a share of the spoils): it was the "vengeance of God." Therefore, the Jewish people had to give a portion of the spoils to the High Priest Eleazar and to the Levites, since they were the "army of God.""
We should learn from this a lesson in the service of God for every Jew. Maimonides explains that the particular matter of the tribe of Levi—being the "army of God"—is relevant to every Jew: "not only the tribe of Levi, but every man... who desires with his spirit, and understands with his intellect, to separate himself and stand before God and serve Him... this person is sanctified as the Holy of Holies and God will be his portion and inheritance.".
A person might think that since he is separate from worldly affairs and sanctifies himself to stand before God and serve Him, what importance does the world around him have?! One should shut oneself away in Torah study and prayer and not get involved in the world and its difficulties.
The reality is that the truth is precisely the opposite of this thought. Precisely because one is part of "God's army," one bears a particular responsibility to join in "God's vengeance against Midian"—to defeat and annihilate those who oppose God.
The name Midian is related to the word madun, Meribah, whose meaning is fighting and arguing, separation, and "gratuitous hatred"—without foundation. This kind of fighting is truly against God, and it is what caused the destruction of the Temple and the bitter exile that continues to this day. Anyone who sees themselves as part of "God's army" must stand before "Midian" and bring Ahavat Israel Love of neighbor, unconditional love, is what unites every Jew with the One God. With this, we hasten the end of the exile, and the true and complete Redemption is immediately revealed with the coming of our righteous Messiah—truly swift.
Extracted from www.chabad.org.il