Yom HaKippurim - Children and Fasting
The ordinance of Yom HaKippurim is, strictly speaking, obligatory only upon adults, since it carries the penalty of being cut-off, and since it is an atonement for sins. However, it is right to subject children to mortification even before their coming of age. This is by analogy of Shabbat, of which it is written, "You will do no work, neither will your son or your daughter" (Shemot [Exodus] 20:10). Therefore, we restrain children from doing work on Yom HaKippurim. We also apply the same rule to mortification of the soul, and extend it to include the little ones. The children, however, should be subjected to it at an age when their lives are not
jeopardized by it - and only to such an extent as they are able to bear. We do this in order to teach them how to observe the day.