Charles Ellicott Commentary Exodus 21:26-27

"And if a man smite the eye of his servant, or the eye of his maid, and destroy it; he shall let him go free for his eye`s sake. And if he smite out his man-servant`s tooth, or his maid-servant`s tooth, he shall let him go free for his tooth`s sake." — Exodus 21:26-27 (ASV)

The eye ... Tooth. —An exception to the law of retaliation is made here. If the injurer is a free man and the injured person a slave, the marked social inequality of the parties would make exact retaliation an injustice. Is the slave, then, to be left without protection? By no means. As the legislation had already protected his life (Exodus 21:20), so it now protects him from permanent damage to his person. The master who inflicts any such permanent damage—from the least to the greatest—loses all property in his slave, and is bound at once to emancipate him. The loss of an eye is viewed as the greatest permanent injury to the person; the loss of a tooth as the least.