The Fast of the Tenth of Tevet
On the tenth day of the month of Tevet, the king of Babylon surrounded the city of Jerusalem in order to destroy it, as the verse in Yechezkel (chapter 24) states: “The word of Hashem was upon me on the tenth month (Tevet) of the ninth year saying, ‘Son of man, write for yourself the name of this day, for on the essence of this day did the king of Babylon besiege Jerusalem.’”
We therefore fast on the Tenth of Tevet in order to humble our hearts into repenting fully and to beseech Hashem to pity us and redeem us completely. The Rambam writes: “The entire Jewish nation fasts on days which tragedy has befallen Israel in order to awaken their hearts and open the pathways of repentance for them. This in turn will serve as a memorial of our grievous actions and the actions of our forefathers to which our current behavior can compare; and this eventually caused suffering to befall them and us. When we recall these things, it will cause us to return to the proper path, as the verse states, ‘And they will confess their sins and the sins of their fathers.’”
Everyone is obligated to fast on the tenth of Tevet, and no one may exclude himself. However, children, meaning boys under the age of thirteen and girls under the age of twelve, are completely exempt from this fast and they are not even obligated to fast for several hours. Even children who are intelligent enough to mourn over the destruction of the Holy Temple are exempt from these fasts as long as they have not yet reached the age of Bar/ Bat Mitzvah. Even if they would like to be stringent and fast, their parents should object to them doing so.
Pregnant and nursing women are exempt from the fast of the Tenth of Tevet and they may not be stringent and fast. The definition of “pregnant” regarding this Halacha is when the woman’s pregnancy is recognizable, meaning when at least three months have elapsed from the beginning of her pregnancy. However, if the pregnant woman suffers from pain and vomiting, she is exempt from the fast even in the beginning stages of her pregnancy, especially if forty days from the onset of her pregnancy have already elapsed.
Pregnant and nursing women are also exempt from the fasts of the Seventeenth of Tamuz and the Fast of Gedalya (their obligation to fast on Tisha Be’av will be explained at the appropriate time, G-d willing). Even if they wish to be stringent and fast, one must object to them doing so. Regarding this Halacha, “pregnant” is defined the same way as above, i.e. when three months of pregnancy have already elapsed. However, if she suffers from vomiting and pain, she is exempt from all of these fasts even before three months have passed, especially if forty days of pregnancy have elapsed.
Regarding the exemption of a nursing woman from these fasts as was mentioned above, Harav Ovadia Yosef zt"l writes that even if this woman is no longer physically nursing her child, if she is within twenty-four months of giving birth and she feels immense weakness, she is exempt from these fasts. However, if she feels no unusual weakness or dizziness and the like, it is proper for her to be stringent and fast. Harav Meir Mazuz Shlit”a, Rosh Yeshivat Kisseh Rachamim, rules likewise. Nevertheless, there are those who rule leniently regarding any woman who is within twenty-four months of giving birth, even if she does not experience any special weakness, that she is exempt from these fasts because she is usually busy dealing with matters of the house and the fast may weaken her.