81:10 I am the Lord your God. Strongly reminiscent of the preamble to the Ten Commandments (Ex. 20:2). The relationship of grace came before revelation of the law.

I will fill it. Much of Israel’s history, as recorded in Joshua through Chronicles, is the story of God’s people looking for satisfaction without God. If they were worried about rain, they turned to Baal (1 Kin. 18). If they were worried about enemies, they wanted a strong king (1 Sam. 8). They kept forgetting they had a God who could and would fulfill all their needs easily.