Musar zu Bamidbar 10:9

The paragraph dealing with the construction of the trumpets and when they are to be blown (10,1-10), describes an "awakening," a recipe how to dispose of the forces of קליפות, the negative forces rampant in the universe, the evil urge. We know from our sages that the blowing of the Shofar on New Year's day is meant to "confuse" Satan, to frighten him into realization that Israel prepares to do penitence (Rosh Hashanah 14). For this reason, the trumpets were blown daily in the Holy Temple, since it is not enough only to offer sacrifices, one must awaken oneself to remorse, confession, etc, in short also do תשובה. This is true even of the יום שמחתכם ומועדיכם, "the day of your joy, or your fixed holidays," since on such occasions a person is apt to relax his usual standards, and the evil urge is more likely to cause him to sin in some fashion. The need for repentance when war comes to our our land is even more pronounced, since success in battle depends on one's being in G–d's good graces, seeing He is the only reliable source of our salvation. Hence the Torah requires the blowing of the trumpets on such occasions.

The words הצר הצורר אתכם, in 10,9, are a fairly clear allusion to the evil urge, seeing there is no other foe that bothers us as much as Satan. We have further support for this view in the unusual construction in verse 9, which speaks about וכי תבואו מלחמה בארצכם, "When war will come to your land." Why is the word תבואו in the plural? We would have expected instead וכי תבוא The allusion here is to the ongoing struggle between man and the evil urge. Sometimes man gains the upper hand in this struggle, at other times the forces of Satan gain ascendancy. At any rate both are constantly involved in a state of war. This is why the Torah uses the plural here. Whenever the community is called upon to perform a collective act such as to come to an assembly or to get ready to journey on it is important that they perform those acts by dedicating themselves to fulfil G–d's commands. The sound of the trumpets then is the rallying cry that helps every Israelite concentrate on what is expected of him. Such dedication is required both at the commencement of an activity and at its conclusion, therefore the Torah repeats על פי ה' יסעו, ועל פי ה' יחנו, "they would journey at the command of G–d, and they would make camp at the command of G–d," in 9,18, whereas in 9,23, we have the same instructions in the reverse order, i.e. על פי ה' יחנו, ועל פי ה' יסעו. The Torah informed us that the departure and the arrival at a site were motivated by the same intentions, namely to carry out G–d's will.