Small tidbits and Sparks of wisdom

וגר לא תונה וגר לא תלחצנו כי גרים הייתם בארץ מצרים
is closely connected with the thought expressed in the preceding verse. There it says that even a native-born Jew of the purest descent forfeits his life amidst the Jewish national community as soon as he departs, in the slightest degree, from the pure basic principle of Jewish worship of God. By contrast, here it says that one who was born a heathen is entitled to complete equality and full rights among Jews under Jewish law from the moment he joins the Jewish fold by accepting the basic principles of Judaism and Jewish worship.
The connection between these two verses marks the great principle, frequently reiterated in Scripture, that personal and civil rights, and personal worth, do not depend on descent, place of birth, or property ownership, nor do they depend on any external, incidental factor that bears no relationship to the individual’s true character. Rather, they depend solely on the individual’s moral and spiritual qualities.
The distinctive rationale כי גרים הייתם בארץ מצרים serves to safeguard this principle against any violation. For the meaning of this rationale is not the same as that of וזכרת כי עבד היית (below, 23:9). Rather, here it says simply and absolutely: כי גרים הייתם. Your whole misfortune in Egypt was that you were גרים there, and that as such, in the view of the other nations, you were not entitled to land, homeland, or existence there, and they could do with you as they pleased. As גרים you were without any rights in Egypt; this led to your עבדות (enslavement) and to your עינוי (affliction). Therefore we are warned: When you have a state of your own, do not make human rights dependent on anything other than the pure humanity inherent in every person. Any deprivation of human rights will open the door to all the abominations of tyranny and abuse that were practiced in Egypt.
גר stems from the root גרה, which is phonetically related to ינה (“to humble,” “to humiliate”), to כנה (“to call something by an incorrect name”), to the Rabbinic term גנה (“to vilify”), and perhaps also to קנה (“to bring under one’s control,” “to acquire”). The root גרה, then, means to illegally deprive of material or spiritual possessions. Thus (a) to defraud in commerce, in purchase or sale, וכי תמכרו ממכר לעמיתך או קנה מיד עמיתך אל תונו איש את אחיו (Vayikra 25:14); (b) to hurt with words in social intercourse, אונאת דברים.
Accordingly, וגר לא תונה would seem to mean: Do not wrong the stranger — neither by words nor by deeds. In Bava Metzia 58b, however, our verse is taken to refer to אונאת דברים. Below, on verses 21–22, which are closely related to our verse, we shall have to focus on the fluctuation between the singular and the plural form of address.