One of the poetic forms in the Hebrew Bible is synonymous parallelism, in which the theme of one line is repeated in a different way in a second line (Roland Kenneth Harrison. Introduction to the Old Testament. William B. Eerdmans Publishing Company, Grand Rapids, Michigan, 1969, p. 966). This verse is the synonymous parallel of the previous verse. The theme of both verses is the binding nature of God’s promise. In the first the permanence was indicated by comparison to a past promise. In this verse, the permanence is compared to the absurdity of the mountains and hills disappearing.