“When you will go out to war against your enemies and Hashem will deliver them into your hand (21:10)” The Posuk stresses “your enemy”. The question is that the word “your enemy” is superfluous, since, when you go to war, you are fighting an enemy? Rabbi Shraga Schneibalg from London Ztz”l gives a beautiful insight to this posuk, and offers a nice connection to the Mishna in Pirkei Avos 4:1 which says “Who is a strong person? He who conquers his Yetzer Harah.” The question is, why does the Mishna stress the word “his Yetzer Harah” and does not simply say “Who conquers the Yetzer Harah?”
He answers that the Yetzer Harah is very different in every person. Every person comes to this world to rectify certain deeds in which he was lax in his previous soul. Therefore, he finds difficulties in serving Hashem in those specific deeds. Each person has a different task to work on and overcome. Therefore, when one sees a friend who the Yetzer Harah has succeeded in luring to his nets, it is not right to tell that person mussar by saying, “I don’t have a problem with the Yetzer Harah in this task, why is it that you can’t overcome the Yetzer Harah?” The answer is simple. Your purpose is not to rectify that deed. However, when it comes to your difficulties with the Yetzer Harah, you see that it is difficult to overcome the Yetzer Harah. Therefore, each person has his personal Yetzer Harah.
That is what the Mishnah is telling us: Who is a strong person? He who conquers “His Yetzer Harah”. When it comes to his difficulties he is then considered a strong person. That is the insight into our posuk which stresses “your enemy”. Go to war against “Your Yetzer Harah” and defeat him.
