Yevamot, Chapter Twelve, Mishnah Four
Halitzah requires what is called daat or awareness/intent. That is both the woman and the man must fully understand that the halitzah permits her to marry others and causes her to become prohibited to the yavam. According to the rabbis, minors and deaf-mutes do not legally have daat (now that deaf-mutes can learn to communicate, they are considered as having daat. Our mishnah rules that deaf-mutes and minors cannot perform halitzah or have it performed to them.
1) If a deaf yavam submitted to halitzah or if a deaf yevamah performed halitzah, or if a halitzah was performed on a minor, the halizah is invalid.
2) If a minor yevamah performed halitzah she must again perform halitzah when she becomes of age; if she does not again perform it, the halitzah is invalid.
Section one: A deaf-mute and a minor can neither perform halitzah nor have halitzah performed upon them. In all such cases the halitzah is invalid and the woman is not free to marry. In the case of a deaf-mute yavam, this would mean that if there are other brothers one of them must perform halitzah. In the case of a deaf-mute yevamah, she could only be released with yibbum (which does not require daat). In the case of the minor yavam, she must have halitzah with another of the brothers (if there are brothers) or wait for the minor to reach majority age.
Section two: The minor yevamah who performs halitzah must perform it again when she reaches age (12 ½). There are other versions of this mishnah which read that in such a case the halitzah is valid. According to this version, although the yavam cannot be a minor, the yevamah can. The reasoning behind this is that the Deut. 25:7 says But if the man does not want, man implying that a minor cannot make such a choice. There is no such word used in connection to the woman, therefore she may be a minor.