We have no idea of the hold the yetzer hara, evil-inclination, has on us, as the following story demonstrates: The Sanzer Rav, Horav Chaim Halberstam, z.l., once stood by his window and gazed at the people walking by. He saw a certain Jew and motioned for him to come inside. When the man entered, the Rav asked him, “What would you do if you discovered a wallet filled with money in the street, and you were aware of the identity of its owner?” The Jew responded, “I would immediately return it.” Hearing this response, the Rav rebuked the fellow and called him a fool.
Another Jew went by, and the Rav called him in and asked him the same question. The second Jew answered, “I would keep it; I am no fool to ‘give away’ so much money.” The Rav scolded him for being a rasha, wicked.
The Rav kept on looking outside until a third Jew walked by. He called him in repeating his question. This Jew’s response was carefully worded, “I do not know what I would do. I guess I have to wait till I am faced with the challenge. My yetzer hara might overwhelm me and ‘convince me’ that I need the money. On the other hand Hashem might help me to break the yetzer hara’s, grasp. As long as I am not confronted with the situation, I cannot give an intelligent response.” This time the Sanzer Rav said, “You gave the correct answer. You possess common sense. We must know the enemy. Only a fool goes into battle without prior knowledge of who it is that he is fighting.”