When God said, “Go from your country, and from your relatives,” he established several new people groups. These groups descended from Abram.
God made a covenant with Abram. This covenant was not conditioned upon anything that Abraham needed to do, but the fulfillment of its promises is conditioned upon the actions of each generation of his descendants. It has not yet been fulfilled in its entirety. (See: rc://en/tw/dict/bible/kt/covenant, rc://en/tw/dict/bible/kt/fulfill and rc://en/tw/dict/bible/kt/promise)
Abram was afraid the Egyptians would see him as a foreigner and upon seeing his beautiful wife, they would try to kill him. This would free Sarai to marry someone else. Apparently, it would have been easy for them to kill a foreigner without punishment. If she was Abram’s sister, they would have shown favor to him. (See: rc://en/ta/man/translate/figs-explicit and rc://en/tw/dict/bible/kt/favor)