Have you ever been a 'foreigner?' In a foreign country, you're constantly aware that you are different. Your customs and your language mean that you never quite 'belong' in the same way as someone who was born into that country and culture. It's a persistent and slightly uncomfortable feeling.
It's curious that Adonai required Abraham to be a foreigner. Abraham was originally from Ur of the Chaldees, a place famous for its culture and it's idolatry. Yet the land Adonai sent Abraham into was also a place where idolatry was practiced.
So if He wasn't moving Abraham away from idolatry, why the change? Was it just because Adonai wanted Abraham to be familiar with Canaan? Other than buying a field in which to bury Sarah, it's not like Abraham ever owned any of the land, so what was the point of moving there?
Could it be that Adonai wanted Abraham to experience being a foreigner? We know for certain that Adonai was in the process of making a new nation, a people who would one day have His law written on their hearts. Did He need Abraham and his descendants to be reminded, daily, that they were different, separate? Yes. Adonai wanted Abraham to be slightly uncomfortable because being uncomfortable keeps you aware.
From time to time we need to ask ourselves, "Have I become too comfortable in my surroundings?" The book of Hebrews records that "By faith [Abraham] sojourned in the land of promise, as in a strange country . . . For he looked for a city which hath foundations, whose builder and maker is God." We, too, need to be aware that we don't belong here. We must live by faith like Abraham did. Like Abraham, we need to look forward to a city whose builder and maker is God.