Exodus 22:21 - Joseph Benson’s Commentary on the Old and New Testaments

A stranger must not be abused, not wronged in judgment by the magistrates, not imposed upon in contracts, nor any advantage taken of his ignorance or necessity, no, nor must he be taunted, or upbraided with his being a stranger; for all these were vexatious. For ye were strangers in Egypt And knew what it was to be vexed and oppressed there. Those that have themselves been in poverty and distress, if Providence enrich and enlarge them, ought to show a particular tenderness toward those that are now in such circumstances as they were in formerly, now doing to them as they then wished to be done to.