In the OT a foreigner is a stranger or resident alien living among the Israelites (Exod. 20: 10), protected by law but obliged to observe the Sabbath. On the other hand foreigners could be a dangerous influence if they were given to idolatry (Isa. 2: 6–8; 1 Kgs. 11: 1) and after the Exile there was a prohibition against marriage to a foreign woman (Neh. 13: 26–7; Ezra 9–10) and an increasing emphasis on the purity of the race.
In the NT believers may be aliens in the world (1 Pet. 2: 11) but are no longer strangers in the Spirit, but citizens with the saints and fellow heirs of God's promises (Eph. 2: 19). The use of foreigner for Gentile continues (Acts 26: 11) and even for a Samaritan (Luke 17: 18).