“Love the stranger” was a unique command to Israel not found in the surrounding religious cultures of the day.  This was rooted in their experience in Egypt.  Egypt extended hospitality to the hungry Israelites strangers.  “Strangers” were also sometimes angels.  “Do not neglect to show hospitality to strangers, for by this some have entertained angels without knowing it” (Hebrews 13:2).  How often was this repeated in the history of the Israelites?  When you get to the NT. the entertaining of strangers became the receiving of the Lord Jesus Himself. This is well illustrated in the story of the Emmas disciples where Jesus was the stranger.  Matthew 25:37-40 illustrates the same thing.  The sheep who ministered to strangers were ministering to the Lord.  Jesus’ total solidarity with all humanity by incarnation is the theology that makes this true.  Never forget that ministry to the alien and the stranger is ministry to Jesus.