1. The Tenth of Tevet marks the beginning of Nebuchadnezzar’s siege on Jerusalem. It also marks the start of the battles which led to the exile from Israel and the destruction of the first temple. We find the date of the tenth of Tevet documented in the words of Ezekiel who was exiled to Babylon 11 years before the destruction of the temple.
2. Besides the Tenth of Tevet we also fast on the 17th of Tammuz, the 9th on Av and the fast of Gedaliah on the 3rd of Tishrei. With the exception of the 9th of Av which is more stringent, these fasts start by dawn and go till night time. We don’t eat and we utilize these days for reflection on our deeds and repentance. We also add special prayers called Selichot pertaining to the fast day and we read the Torah portion of Vayichal Moshe (“And Moses pleaded before the Lord”).
3. The Tenth of Tevet is actually the third consecutive day that bad things happened to our nation. On the eighth of Tevet the Torah was translated to Greek under the orders of King Ptolemy and this diminished the stature of the Torah. On the ninth of Tevet, Ezra and Nechemia the leaders of our nation died and the eyes of the nation that had just come back from exile darkened. And, as we mentioned, on the tenth of Tevet the siege on Jerusalem began.
4. In the year 3338 Nebuchadnezzar the king of Babylon laid siege on Jerusalem with his troops to starve its inhabitants and conquer it. (Kings 2 25). The Midrash Tanchuma on the Torah portion of Tazria explains that “we were supposed to be exiled on this day the Tenth of Tevet but because of the cold weather G-d waited until the summer to exile us.” This Midrash shows G-d’s love for us and great compassion for His children; even when they sin- G-d still considers the weather before sending them to exile and waited till the summer.
5. The chief rabbinate of Israel declared the Tenth of Tevet the national day of kaddish for all holocaust martyrs for whom the date of their death was unknown.
6. Our fast days are for the purpose of repentance and improving our actions so that G-d will have mercy on us and bring us the complete redemption.
7. In the “Book of our Heritage” it says: “Pain and mourning is not the main part of a fast day… rather the main part of a fast day and its purpose is to arouse the hearts and open paths to repentance.”
8. According to the Abudraham, if the tenth of Tevet would fall on Shabbat we would fast which is unique to this fast. Other fast days including the stringent 9th of Av would be deferred to Sunday. The source of this is the verse in Ezekiel “this very day”. The reason this fast has this stringency is that “this day is more difficult that the destruction of the temple; it is a sign marking that a great calamity befell us and all beginnings are difficult.”
It should be noted that the Tenth of Tevet never falls out on Shabbat (or on Monday) according to our Jewish calendar so the stringency of the Abudraham is not actually practiced. However, other fasts that fall out on Friday also get pushed to Sunday but when the Tenth of Tevet falls out on Friday we still fast and do not defer it to Sunday.
9. The Hatam Sofer says: “Any generation the temple is not rebuilt in is considered as if that generation destroyed it. This means every year it’s considered another new destruction and on the Tenth of Tevet the judgment in heaven about the destruction originally took place on this day gets repeated and a new heavenly judgment takes place to judge destruction for that year. That is why the 9th of Av which is only about the past destruction gets deferred by Shabbat but the Tenth of Tevet which is always about a new future destruction doesn’t get deferred by Shabbat.” (Hatam Sofer on the Torah, Levitcus)