It is in the discussion of organizing and managing the spoils of the successful military campaign against Midyan that the Torah reveals to us the rules of purging dishware and cookware and the obligation to bring them all to tevilah in a mikva. Whereas purging is a technical chapter in the laws of kashrus making sure that we avoid eating from the absorption of non-kosher foods, tevilas keilim is a different matter altogether. Tevilas keilim is according to most rishonim an independent Biblical mitzvah, and this is the first time it was being taught to us.
Whether first taught after this battle or first recorded, there must be some message in our studying the mitzvah of tevilas keilim in response to the battle with Midyan rather than in the common presentation of a directive to Moshe to teach as other halachot appear, with notable but rare exception.
To be sure the war against Midyan was unusual. We are certainly familiar with battles that have been waged in our defense, such as against Amalek and against the armies of Sichon. We also understand that we are commanded to battle in order to establish the Land of Israel as our home. Yet the battle of Midyan was neither to remove a present threat nor to ready land for our families. It is presented as revenge for the diabolical strategies of Bilam that were exercised by Midyanites. (Bamidbar 2:18, Rashi)
True their battle against us brought us to one of the lowest points of the midbar narrative. Women were sent into our ranks and first encouraged familial infidelity which in turn led to serving peor, a service which defiles human conduct and religious service as well. This ultimately led to the public repudiation of no one less than Moshe Rabeinu and all he stood for by one of the tribal leaders. Additionally, the encounter introduced the coupling of infidelity with idolatry, a theme that Yirmiyahy Hanovi would often revisit in warning us of the impending destruction of the first Beis Hamikdosh.
Remarkably, Moshe is told that the battle against Midyan is to be waged neither because of the idolatry nor because of any loss of life nor because of the rebellion that it brought about, rather because they sought to undermine our familial relationships (Bamidbar, ibid). Bilam is recorded to have advised Midyan that our G-d hates decadence and introducing it to our people was Midyan's surest manner of affecting a military like victory.
For our people, going to war for a cause is probably the strongest statement that could be made in advocating its centrality to our thinking. Thus this war indicates that our existence is dependant on a healthy family structure. That infidelity and idolatry are so closely associated further emphasizes that when integrity and loyalty are trampled we remain without anchor or purpose. The converse that truthfulness and faithfulness are necessary for the successful transmissions of our legacy as individuals and as a people is boldly stated by our battle against Midyan.
Clearly to remind ourselves of the importance and preciousness of the family and its attendant relationships and attitudes through the study of a onetime battle will have little impact. After all, creating the warmth and the vibrancy of a successful home and family requires unflagging patience, sincere respect and an ongoing commitment to cheerfulness (Rambam, Ishus 1:19). It demands the utmost respect for home making and home makers, unquestionably challenging in a two income family climate.
Perhaps setting the mitzvah of tevilas keilim into the context of the bold statement of the Midyan battle underscores the mitzvah as an enduring reminder of what we fought for so long ago. Thus we announce the uniqueness and sanctity of the Jewish family whenever introducing any table and cooking utensils of non-Jewish origin into homes (Talmud Yerushalmi, Avoda Zara 5:15). Hopefully this will instruct us to be ever mindful of the efforts required to make a home the haven that it must be for growth in faith and character, and accord absolute respect for all those efforts and their dedicated providers.