997. The Age of Majority

Shvisas Asor 2:11

A girl 12 years and one day old and a boy 13 years and one day old, who have two pubic hairs, are considered to be adults when it comes to mitzvot and they are obligated by the Torah to complete the Yom Kippur fast. If they do not have the signs of maturity, they are still considered minors and are only required to complete the fast by rabbinic law. A child under the age of nine should not be afflicted with fasting at all on Yom Kippur out of a concern that it might prove hazardous.

Shvisas Asor 3:1

We are not permitted to wash on Yom Kippur, neither with hot water nor cold. One may not wash his entire body, nor even one limb. One may not even immerse his little finger in water. A king and a bride are permitted to wash their faces - a bride so that she will not be unattractive to her husband, and a king so that he will appear impressive as per Isaiah 33:17, “Your eyes will behold the king in his splendor.” A new wife is considered a bride for 30 days.