מבן עשרים שנה ולמעלה, “from twenty years old and up.” Bemidbar 1,3
The reason that the under twenty-year olds were not included in the census was because they were not yet strong enough physically to be recruited for army duty. This is reflected in the statement by our sages in Avot, 5 (near end) that at twenty one is strong enough to engage in pursuit (of an enemy).
לצבאותם, “according to their hosts.”
There were many different hosts (armies). Every single tribe had a substantial army.
A Midrashic approach based on Tanchuma Bamidbar 19: the words “count them according to their hosts,” are reminiscent of Isaiah 43,4: “because you are precious to Me, and honoured, and I love you, I have given men in exchange for you and peoples in your stead.” G’d said to Yaakov: “you are so precious in My eyes that I have engraved your facial features on My throne, and the angels praise Me by employing your name, saying: ‘blessed be the name of the G’d of Israel from one end of time to the ultimate end of time.’” The Midrash breaks down these compliments into its constituent parts. “You are precious to Me,” because although I did not bother to count any of the other nations I counted you, giving you an importance expressed in numbers.“
This can be better understood in terms of a parable. A king had many barns most of which were filled with straw and other relatively worthless matters. He did not bother to count the precise contents of each of these barns. He had one barn, however, which was filled with wheat. He told his manager: “count for me how many measures of wheat are stored in that barn.” The king in the parable is a metaphor for G’d; the wheat is a metaphor for the Jewish people. We have a verse in Isaiah 21,10 comparing the Jewish people to grain when the prophet exclaims: “My threshing, the product of My threshing floor.” The harvest the prophet speaks about are the Jewish people as Jeremiah 2,3 described the Jewish people as “Israel is sacred to G’d, it is the first of His harvest.” The “manager” mentioned in the parable is a metaphor for Moses, of whom G’d Himself said in Numbers 17,7 that in “My entire house he is trusted.” Similarly, the barns filled with straw in the parable are metaphors for the Gentile nations concerning whom we have been told in Job 21,18: (Job speaking about the wicked) “Let them become like straw in the wind, like chaff carried off by a storm.” we also have a verse in Ovadiah 18 expressing similar sentiments, i.e. “and the house of Esau shall be straw; they shall burn it and devour it.” The Jewish people by way of contrast are compared to wheat, are described as righteous as per Isaiah 60,21: “and Your people, all of them righteous, shall possess the land for all time; “ this is why G’d was so concerned with each one of them that He ordered each one to be counted.
איש על דגלו באותות, “each man by his flag according to the insignia.” BeMidbar 2,2
A kabbalistic approach: the Israelites wished for flags similar to those of the angels. The division of the Israelites’ camp into four sections comprising three tribes each facing each direction on earth reflected a similar phenomenon in the celestial regions. The four celestial camps are known as the camps of the Shechinah (Midrash Maasseh Merkavah chapter 6). The tribes of the Israelites in addition had twelve maps, each one differently colored and easily identifiable one from the other. This too reflected what they had observed when the angels had come to earth when these “maps” were in the form of fiery flames each differently colored.
Yehudah’s map was blue like the sky, featuring the picture of a lion; Issachar’s map was similar to the blue eye shadow used by women, featuring images of the sun and the moon; this reflected the fact that this tribe was famous for its knowledge of astronomy, calendar calculation, etc. Zevulun’s map was white in color, symbolizing silver, wealth; it also had a picture of a ship on it seeing that tribe had many mariners. Reuven’s map was red, featuring pictures of דודאים, mandrakes or jasmine, reminding the tribe of how their ancestor had traded these to Rachel. Shimon’s map was green, with a picture of the town of Shechem. Gad’s map was a mixture of white and black, featuring a troop of soldiers. Ephrayim and Menashe both had maps of the color of onyx; the map of Ephrayim featured the picture of an ox, whereas that of Menashe featured the picture the animal known as ראם, single-horned buffalo? Binyamin’s map was colored like a rainbow showing the picture of a wolf. Dan’s map was like a sapphire in color displaying the picture of a snake; Asher’s map was similar to the light emitted from an olive-oil burning lamp and displaying the picture of an olive. Naftali’s map was of the color of clear (red) wine, displaying a hind.
