Midrash su Isaia 44:5

(Exodus 22:20) "And a stranger you shall not afflict and you shall not oppress him": You shall not afflict him with words and you shall not oppress him in money matters. Do not say to him: "Yesterday you worshipped the deity of Nevo, and (the flesh of) swine is still between your teeth, and you would dare contend with me!" And whence is it derived that if you taunt him he can taunt you in return? From "And a stranger you shall not afflict … for you were strangers in the land of Egypt" — whence R. Nathan derived "Do not attribute a blemish of your own to your neighbor." Beloved are the strangers, for in many places you are exhorted concerning them: "And a stranger you shall not afflict", (Devarim 10:19) "And you shall love the stranger", (Exodus 23:9) "And you have known the soul of the stranger." R. Eliezer says: Because a stranger's past is to his disadvantage, Scripture exhorts concerning him in many places. R. Shimon b. Yochai says: It is written (Judges 5:31) "And His lovers are like the rising of the sun in its might", and it is written (Devarim 10:18) "And He loves the stranger, etc." Now who is greater? One who loves the King or one whom the King loves? Certainly, one whom the King loves. Beloved are the strangers, for by every epithet that Israel is called, the strangers are called. Israelites are called "servants," as it is written (Leviticus 25:55) "For unto Me the children of Israel are servants." And the strangers are called "servants," as it is written (Isaiah 56:6) "… to love the name of the L rd and to be servants unto Him." Israelites are called "ministers," as it is written (Ibid. 6:6) "And you, 'priests of the L rd' shall you be called; 'ministers of our G d' will it be said of you." And the strangers are called "ministers," as it is written (Ibid. 56:6) "… and the strangers who join the L rd to minister unto Him." Israelites are called "lovers," as it is written (Ibid. 41:8) "the seed of Abraham, My lover." And the strangers are called "lovers" (i.e., beloved), as it is written (Devarim 10:18) "And He loves the stranger." "Covenant" is written of Israel, viz. (Genesis 17:13) "And My covenant (i.e., circumcision) shall be in your flesh." And it is also written of strangers, viz. (Isaiah 56:4) "and they hold fast to My covenant." "Acceptance" is written of Israel, viz. (Exodus 28:38) "for acceptance for them before the L rd." And "acceptance" is written of strangers, viz. (Isaiah 56:7) "their burnt-offerings and their sacrifices for acceptance upon My altar." "Watching" is written of Israel, viz. (Psalms 121:4) "He neither slumbers nor sleeps, the Watcher of Israel." And "watchers" is written of the strangers, viz. (Ibid. 146:9) "The L rd watches the strangers." Abraham called himself a stranger, viz. (Genesis 23:4) "A stranger and a sojourner am I with you." David called himself a stranger, viz. (Psalms 119:19) "I am a stranger in the land," and (I Chronicles 29:15) "For we are strangers before You and sojourners as all of our ancestors. As a shadow are our days upon the earth, without a prospect." And it is written (Psalms 39:13) "For a stranger am I with You, a sojourner as all of my ancestors." Beloved are the strangers (i.e., the proselytes), as witness Abraham's not being circumcised until the age of ninety-nine. For if he were circumcised at twenty or thirty, a stranger could become a proselyte only if he were younger than thirty — wherefore the L rd prolonged commanding him until he was ninety-nine, so as not to bar the door to future proselytes. And thus do you find (the L rd's esteem for the stranger-proselyte) in the four classes who respond before Him who spoke and brought the world into being, (Isaiah 44:5) "One shall say: 'I am the L rd's'; another shall call in the name of Yaakov; another shall mark his arm 'of the L rd'; and in the name of Israel he shall be called": "I am the L rd's" — these are the fearers of Heaven, untainted by sin. "another shall call in the name of Yaakov" — these are the minors (who died in childhood), the sons of the wicked in Israel. "another shall mark his arm 'of the L rd'" — these are the penitents. "and in the name of Israel he shall be called — these are the righteous strangers (i.e., the proselytes).