The Lord now moves to specifics of the way the righteous should seek. Recognizing their relationship with the covenant and law of God, they must look to that law. The Lord makes a comparison of his gospel to the world around Israel. They may look to the elements of the physical world, and may think that they will endure forever. All mankind looks to the physical world, and it changes so slightly that it appears eternal. The mountains continue. The sky continues.
Nevertheless, the Lord notes that all of these things of seeming permanence will eventually "vanish away like smoke." The world will come to an end, but the salvation of the Lord truly is forever. Even with the mountains are no more, the gospel will be.