Read Isaiah 55 and then see John Stott's insight on this passage....
Christianity is essentially a revealed religion. We would know nothing about God if he had not made himself known. This is especially true of God's gracious character. He offers a free drink to the thirsty, a free place in the covenant to the nations, and a free pardon to the wicked. (v.1-7). Who could have invented such a gospel of grace? It is too good to be true!! It could be known only by divine revelation. Consider its logic.
FIrstly, Yahweh's thoughts are inaccessible to us. They are as much higher than our thoughts than the heavens are higher than the earth. Our little minds cannot climb up into the infinite mind of God (vv.8-9).
Secondly, Yahweh's lofty thoughts must come down to us as the rain and snow come down from heaven to earth (v.10).
Thirdly, Yahweh's thoughts have in fact been brought within our reach because they have been put into words. Thus human speech is the model of divine revelation. It is by the words of our mouth that we communicate the thoughts of our minds. We cannot even read each other's minds unless we speak; how much less can we read God's mind unless he speaks? And God has spoken, his word has come down to us.
Fourthly, Yahweh's word is powerful; it always achieves its purposes (vv.10-11).
The last two verses of the chapter (vv.12-13) describe in vivid Hebrew poetic imagery the immense blessings enjoyed by the people of God who have received the word of God. They experience a new exodus (v.12), and they inherit a new promised land (v.13). No wonder we are filled with joy and gladness. See 1 Corinthians 2:6-10.