Mishnayos Kiddushin Perek 1 Mishnah 3

עבד כנעני נקנה בכסף ובשטר ובחזקה – As it is written (Leviticus 25:46): “You may keep them as a possession for your children [after you], for them to inherit as property…,” they (i.e., the Rabbis) made an analogy [on a principle common to both between] עבדים /servants to קרקעות/property. Just as property is acquired by money, document and/or claim based upon undisturbed possession [during a legally fixed period], so also, a Canaanite slave is acquired by money, document and undisturbed possession. And the undisturbed possession of the [Canaanite] slave, such as that he unloosed the shoe for his master, or he helped him put on his shoe, or carried his utensils after his master to the bath house, or undressed him, or washed him, or anointed him, dragged [his possessions], or dressed him, or lifted him up or the master lifted up the slave, he has acquired him.

בכסף על ידי אחרים – and they will give it (i.e., the money) to the Master in order that this one (i.e., the Canaanite slave) will be a free person, but he himself cannot receive from them, and even on the condition that the Master does not have control over him, since he holds that there is no acquisition for the slave in any side without his Master [being involved].

ובשטר ע"י עצמו – For he holds that is obligatory for the slave that he leave from under the hands of his master to freedom, for if the slave is of a Kohen, this disqualifies him from eating the Priest’s due, and if the slave is of an Israelite, it prohibits him from [marrying] a slave/handmaid; and because of this it is said that he does not go out to freedom with a document from/by others, but only by himself, and because it is an liability for him, we do not act on behalf of a person to the latter’s disadvantage other than in his presence (see Mishnah, Tractate Eruvin, Chapter 7, Mishnah 11). And [through] money, which is via others, is different, for the acceptance by the master causes him to be liberated on his own, and these others cannot act on behalf of a person to the latter’s disadvantage, other than through the acceptance of the master, for the master is not made into his agent, but rather, for the needs of himself, and who transfers [possession] on his own.

וחכ"א בכסף ע"י עצמו – for they hold that there is acquisition for the slave without his master; therefore, he acquires himself through money, even through himself, and all the more so, through others.

ובשטר ע"י אחרים – as they hold that it is a benefit to the slave that he would go out from under the hand of his master to freedom, and we do something for another’s benefit in his absence. And the Halakha is according to the Sages. But the Canaanite slave acquires his [freedom] if his master blinded his eye or caused him to lose a tooth or mutilated from him one of twenty-four heads of limbs, which are [the tops] of the fingers of the hand, and digits of the feet, and the tops of the ears, the head of the nose, and head of the male genitals, and the tops of a woman’s breasts, and that which is not considered in our Mishnah to be included in those things that the slave acquires himself, because one who goes free through the tops of his limbs requires a document of manumission from his master, that is, that he acquires himself through a document.

ובלבד שיהא הכסף משל אחרים – for a slave has nothing, for even what he finds and/or receives as a gift – everything belongs to his master. And if he came to be redeemed by himself, the monies must come from others who would give it him on the condition that his master has no control over him.