פּירוש אויף דברים 19:21

עין בעין EYE FOR EYE — i.e. monetary compensation; similarly also “tooth for tooth” etc. (Sifrei Devarim 190:16; Bava Kamma 84a; cf. also Rashi on Exodus 21:24).

you must not show mercy upon the false witness.

ולא תחוס עינך, “and your eye shall not display pity.” You shall not have pity with the guilty person; on the other hand, even during war time you shall display pity on people who are in the process of building their homes for the first time, be it that they are engaged to be married, that they are in the middle of building a house, or planting an orchard. The Torah teaches you a lesson here of when it is appropriate to display pity and concern, and when not. This is why these two paragraphs one dealing with expansionist wars, the other about people undermining faith in the Lord of their brethren, follow one another in the Torah.