Êxodo 21:8 Referências da Mishná: Mishnah Kiddushin & Mishnah Bekhorot

A Hebrew slave is acquired by money and by document; And acquires himself by years, by Jubilee, and by deduction from the purchase price. A Hebrew maidservant is greater in that she acquires herself by ‘signs [of physical maturity]’. He whose ear is bored is acquired by boring, and acquires himself by Jubilee or his master's death.

If he does not wish to redeem it, he breaks its neck from behind with a large knife and buries it. The mitzvah of redemption takes priority over the miztzah of breaking its neck, for it says: “And if you don’t redeem it, you must break its neck” (Exodus 13:13). The mitzvah of designation takes priority over the mitzvah of redemption, for it says: “Who has betrothed her to himself, he must let her be redeemed” (Exodus 21:8). The mitzvah of yibbum is prior to the mitzvah of halitzah. [This was so] at first when they intended to carry out the mitzvah. But now that they do not intend to carry out the mitzvah, the [rabbis] have said: the mitzvah of halitzah takes priority over the mitzvah of yibbum. The mitzvah of redemption [of an unclean animal whose value has been dedicated to the Temple] is upon the owner. He takes priority over any other man, for it says: “If it is not redeemed, then it shall be sold according to your evaluation” (Leviticus 27:27).