Towards the beginning of the Parsha we read about the war against Midian. 12,000 soldiers, 1,000 from each tribe, were sent to exact vengeance from the Midianites for causing Bnei Yisroel to go astray. The soldiers returned to the camp with all of the spoils from their victory, including food vessels.
Upon their return, Elazar instructed them that all metal vessels captured would require Kashering, to purge them from any non-Kosher taste that they had absorbed when used by their former owners.
From this episode the Gemara derives many of the important principles governing the laws of Kashrus. Aside from the actual Kashering procedures, we learn the concept of Taam K’Ikar. This means that not only the actual substance of non-Kosher food is Biblically forbidden, but also the taste that is imparted by forbidden foods. This applies even to the “taste” that has been absorbed into the walls of a pot in which non-Kosher food was cooked. This ‘taste’ must be extracted or removed through the various methods of Kashering.
The Talmud (Shabbos 64b) relates how Moshe became angry at the soldiers. Since they had not killed the Midianite women (who were the ones responsible for causing Bnei Yisroel to sin), Moshe suspected that the soldiers continued to act immorally with them.
The soldiers protested that they were all righteous and free of wrongdoing. But Moshe was unconvinced. The returning soldiers had expressed their wish to offer some of the spoils to seek atonement. Moshe argued that if they were indeed guiltless, why was atonement necessary? The soldiers replied that whilst they did not act improperly, they had nonetheless had sinful thoughts.
The Kotzker Rebbe asks how the soldiers derived that one must atone for thoughts of sin, when the Torah doesn’t require a Korban for sinful thoughts.
