Chapters 21-23 contain  various social laws.  We note Ex 22:21:

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          "Do not mistreat an alien or oppress him, for you were aliens in Egypt."

          

The command to treat fairly aliens who live among the Israelites is repeated many times throughout the Old Testament.  The rationale is based on the Israelites' own bitter memories of Egypt.  Sometimes, the following principle is appended: "You must have the same regulations for the alien and the native-born" (Num 9:14, Num 15:15-16). This was an extraordinary concession to non-covenant people, and it cut through any tendency of Israelites toward racial pride.  They were not to create a racially stratified society.  Aliens were not slaves or prisoners of war, they were resident freeborn foreigners who agreed to abide by the social laws of Israel.  They may be seen as forerunners of the promise to Abraham that all nations would count themselves blessed in him.