The Fast of the 10th of Tevet is here. No need to introduce the Yetzer Hara (evil inclination). It's an old acquaintance. A twin brother, a Siamese twin, whose life we share from birth. If someone asked us where it resides, we could easily respond: "It's redundant. It squats permanently in our hearts".

It would seem like the Yetzer Hara is in the heart region, but this is just an optical illusion. The Gemara says: "The evil inclination may be compared to a fly sitting between the heart’s ventricles. Thus, we learn it resides outside of our hearts. If we believe it lives inside our hearts it’s just because we have opened the doors for it”.

An old adage stipulates: “The evil inclination cannot climb a smooth wall”. It waits at the bottom for someone to open the doors or at the very least throw a rope for it. A verse in Genesis (4,8) says: “Sin is crouching behind your door”. It waits patiently at a standstill for the adequate moment to assail us and take advantage of our weaknesses. As a fly, desperately searching for an open wound.

A different but no less accurate interpretation elicits the location of the evil inclination outside of the heart: the Fast of 10 Tevet best supports this understanding. As written in the book of the Prophets:" It came to pass that on the 9th year of his reign, on the tenth month (according to the counting of the months starting in Nissan), Nebuchadnezzar, King of Babylon camped around Jerusalem with his army and built a dike around the city.  Thus, they besieged Jerusalem causing a famine amid the population; there was no bread to eat and the city was stormed(Kings II, 20, 1-4).

Our Sages established a fast on the month of Tammuz when the walls of the city were first breached. Same for the day of the destruction of the Temple, known as the fast of 9 of Av. But a special fast day was decreed for the day when the siege of Jerusalem began. Although at that moment, the food stock was full, the pantries were crammed and the population was satisfied.

Why Did Our Sages Institute this Fast for the Coming Generations?

In fact, the city fell on the 10th of Tevet! Because Jerusalem’s sentence began as soon as the city was besieged. Cut off from its fields of grain and its fruit trees, all of Jerusalem’s sustenance depended on products imported from outside the walls. Thus the Babylonian siege had stamped its decree unless an extraordinary event could reverse it.

Considering this reminder, we gain a better understanding of what has been said on the evil inclination lurking in the shadows: it imposes a siege upon us! The Zohar Hakadosh compares the heart of man to the city of Jerusalem. The heart, just like the city of Jerusalem, needs spiritual food, administered from outside. It owns neither fields of grain nor fruit trees to rely upon. It is nourished from sources found in its periphery: Torah classes, prayer and the practice of Mitzvot - all these elements compose its basic diet and indispensable sustenance.

How does the Yetzer Hara work? It occupies a sophisticated seat, settled between the ventricles of the heart. It does not wait for the doors to open. Sometimes it even ensures they remain locked! And it sabotages the arrival of vital convoys, discouraging us from attending Torah classes, praying or practicing Mitzvot. If we surrender to the siege imposed by the evil inclination, we lose the war and therefore our central artery, feeding the "Jerusalem" of our heart. The only escape is to break the siege: attend Torah classes, increase the practice of Mitzvot, fill our hearts with spiritual inspiration, lectures, and uplifting books. Thus, we may heroically resist the implacable siege of the Yetzer Hara, impeding it from storming our fortress!