Isaiah 5:24

"Therefore as the tongue of fire devoureth the stubble, and as the dry grass sinketh down in the flame, so their root shall be as rottenness, and their blossom shall go up as dust; because they have rejected the law of Jehovah of hosts, and despised the way of the Holy One of Israel. Therefore is the anger of Jehovah kindled against his people, and he hath stretched forth his hand against them; and the mountains tremble, and their dead bodies are as refuse in the midst of the streets. For all this his anger is not turned away, but his hand is stretched out still."

The big thing in this paragraph is the clear statement of the reason why God's judgment and destruction of Israel were proclaimed here as already predetermined and certain to occur, the past perfect tenses used here being the Biblical tenses of prophetic certainty.

Sinful men who have rebelled against God's government and who stubbornly continue their wickedness are on a collision course with disaster, determined and foretold from the foundation of the world and absolutely impossible of avoidance.

The mention of "God's law" is a reference to the Pentateuch without any doubt whatever, thus categorically giving the lie to all theories about the Pentateuch having been derived from the post-exilic works of Jewish priests.