(Tamid 32a): "איזהו חכם הרואה את הנולד"—a truly wise person foresees the consequences of all his actions. He realizes that if he sins, he will ultimately be held accountable. Therefore, he does not fall prey to sin; and if he does sin, he performs teshuvah. When the yetzer hara persuades a person to commit an aveirah, the “wise” yetzer tov provides moral support. It encourages him not to be swayed or enticed by the glittery nonsense that surrounds us in Olam HaZeh. It helps a person realize that he is being deluded by his desires and cravings and will suffer the consequences. Instead, he sees the world with open, intelligent eyes; he realizes that ultimately we are all destined to die and that nothing will remain of the meaningless desires of Olam HaZeh.
Furthermore, because of the sensible, positive influence of the yetzer tov, a person realizes that HKB”H will hold him accountable for all of his actions. In the words of the Tanna, Akavya ben Mehalalel (Avos 3, 1): "ולפני מי אתה עתיד ליתן דין חשבון לפני מלך מלכי המלכים הקדוש ברוך הוא"—(know) before Whom you will be held accountable . . . Before the King of Kings, HKB”H.
By considering future consequences, a person will avoid committing an aveirah. For this reason, the yetzer hara is depicted as a foolish, old king; because it introduces foolish whims in a person’s mind that confound and displace his wisdom. Thus, he does not consider future consequences; instead, he is enticed by the glittery appeal of the present.
The explains beautifully a passuk in parshas Ha’azinu (Devarim 32, 28): "כי גוי אובד עצות המה ואין בהם תבונה, לו חכמו ישכילו זאת יבינו לאחריתם"—for they are a nation bereft of counsel, and there is no understanding in them. Were they wise, they would have comprehended this, they would have understood from their end.
In other words, the root cause of sin is not heeding the advice of the yetzer tov—the "חכם"—to consider the end result of an action--"לאחריתם"—like a “wise man who foresees the consequences.” For, if people truly understand the consequences of their actions, they will not fall into the yetzer hara's trap; they will realize that it does not pay to sin.
We can now explain the end of the feat of the staff: Hashem said to Moshe, “Stretch out your hand and grasp its tail.” HKB”H hinted that the best strategy when dealing with the yetzer hara is to grab it by its tail. In other words, emulate the wise man who considers the consequences of his actions. Do not look merely at present appearances but consider the matter all the way through, including future developments and ramifications. Realize that all matters of Olam HaZeh are merely empty, deceptive, false illusions.
He stretched out his hand and grasped it tightly, and it became a staff in his palm. Then, “he stretched out his hand and grasped it tightly, and it became a staff in his palm”—by taking the future into consideration, he once again had a staff in the palm of his hand with which to strike the yetzer: “So that they shall believe that Hashem, the G-d of their forefathers, appeared to you, the G-d of Avraham, the G-d of Yitzchak and the G-d of Yaakov.” This convinced the people that Moshe was their legitimate savior, since the source of the holy Avos’s strength was their constant vigilance. They were always ready to battle the yetzer hara. In this merit, they succeeded in establishing the house of Yisrael, a people that would follow in their footsteps, until the end of time.
