Rashi in verse 23 says that Sichon declined the overtures of peace, as all the Canaani nations paid taxes to him, to protect them from armies passing through his land to wage war against them. When the Jewish People said to him: “Let us pass through your land,” he replied: “My very presence here is to protect them from you and you say this?” The Gur Aryeh observes that earlier the Edomi, who were not paid to protect Canaan, also refused the Jewish People passage (20:18-21). Yet Rashi attributes Sichon’s refusal to the protection payment. What was the difference? The answer is that the Edomi request was based on brotherhood (20:14), thus assuring Edom that the Jews would not wage war if they refused, since they were distant cousins. Sichon certainly understood that his refusal would be met with an attack, yet he accepted the consequence of warfare, because he had been paid to do so. (Click here and here for Hebrew text.)
What was his motivation? Rashi goes out of his way to point out he was being paid to defend the Canaani nations. It would seem, therefore, that if they had not been paid and only treaty or agreement to protect each other had been in place, he would have succumbed to the request of the Jews to peacefully travel through his land (in order to not face guaranteed conquest, which is what, in fact, happened). Yet, because he was paid to defend them, he decided to attack the Jewish people, which was his ultimate downfall. Why did he choose this route, with its guarantee of failure?
I heard firsthand from my Rosh HaYeshiva ztk”l, Rav Henoch Leibowitz, that it is better to hire people to work for you than to find volunteers, because paid workers feel more of a responsibility to get the job done correctly.
This is what Rashi is pointing out in this situation. Because Sichon was being paid, he essentially had a duty to defend the other nations, and he felt a responsibility to live up to this expectation. Although this was ultimately his downfall, the power of money is a fact and can be used in a positive way throughout our lives. Organizations and businesses run better with paid workers. Institutions and schools are more organized and professional with hired help. Even household needs are met more efficiently with hired help, most of the time.
Money, in a positive sense, brings with it a sense of responsibility which potentially could get a lot of good done in the world, if used wisely.