“And all the trees of the field will know that I Yahweh have brought down the high tree, have exalted the low tree, have dried up the green tree, and have made the dry tree to flourish. I Yahweh have spoken and have done it.”
Some refer the high tree and the green tree to Assyria and Egypt, but in the parable the tree represented Israel. The point is that Israel who exalted themselves, and who claimed to be the living tree, will have been brought down, but the low and dry tree, which represents the despised remnant faithful to Yahweh (compare Isaiah 6:13), will flourish. Compare for the idea Isaiah 53:2.
‘I Yahweh have spoken and have done it.' This crowns the chapter. All that will happen will result from the word of Yahweh (see Isaiah 55:11).