Commentary for Exodus 21:27

ואם שן עבדו….יפיל, And if he smite a tooth of his slave…. so that it falls out, etc. Kidushin 24 explains why the laws concerning destroying a slave's eye or tooth are not lumped together by the Torah in one verse but have been divided into two separate laws. Rabbi Sheshet says if the eye of a slave was already blind but the master gouged it out, the slave has to be freed. Accordingly, we have two separate laws concerning how to free a slave. One applies when the eyesight of the slave has been impaired as a result of the master hitting him, the other if even a blind eye has been scratched out by his master. Had the Torah lumped these two kinds of injuries together in a single verse, we would have concluded that the same yardstick is applied in either kind of injury. Just as the tooth becomes useless only when it is knocked out, so we would have thought that an eye becomes useless only when it is gouged out. We would not have assumed that destroying merely the sense of sight in an eye was sufficient reason to let the slave go free seeing the slave did not lose a limb.

ישלחנו, he will release him. The expression שילוח, is similar to the when we read in Deuteronomy 24,3: ושלחה מביתו, “he sends her away from his house;” the reason that the word: חנם, “without any compensation is absent here is the reason why the word: חנם “without compensation,” is absent here in our chapter, [as opposed to verse 11 in our chapter, where automatic release of slaves after 6 years service is discussed Ed.], is to teach us that the release must be accompanied by a document just as the document of divorce to a wife.