וְגֵ֥ר לֹא־תוֹנֶ֖ה וְלֹ֣א תִלְחָצֶ֑נּוּ כִּֽי־גֵרִ֥ים הֱיִיתֶ֖ם בְּאֶ֥רֶץ מִצְרָֽיִם׃
And a stranger shalt thou not wrong, neither shalt thou oppress him; for ye were strangers in the land of Egypt.
Read kabbalistic (mystical) interpretation of Exodus 22:20: and classical mystical sources.