What does Genesis 22:18 mean?

In the previous verses, the Lord declared that He had sworn "by Himself" to do for Abraham several very specific things. Those included blessing Abraham, multiplying his offspring enormously, and giving his offspring victory over their enemies.

Now the Lord adds one more promise that applies to everyone who might read these words. The Lord says that in Abraham's offspring, all the nations of the earth will be blessed. This promise, too, is repeated from previous interactions with the Lord (Genesis 12:3; 18:18), with the addition that this blessing on the peoples of the earth will come through Abraham's descendants and not merely through him.

How will this happen? Most significantly, the offspring of Abraham will lead through Isaac to Jacob and down through history to Jesus Himself. All the peoples of the earth have the opportunity to be saved from sin and included in God's family through faith in Abraham's offspring Jesus (Galatians 3:7).

This verse concludes that the Lord will do all of these things because Abraham has obeyed the Lord's voice. It's interesting that the Lord made all of these promises to Abraham without any condition in earlier encounters. Then, the promises were given merely because God wanted to give them. Now, Abraham's obedience is included as a reason for these gifts from the Lord.

It's beautiful circle. The gifts are given unconditionally by the grace of God. The receiver of the gift recognizes God's goodness and obeys God's commands. God now cites the receiver's obedience as reason to give the gifts He would have given, anyway.