And He said, Go, and tell this people, Hear ye indeed, but understand not; and see ye indeed, but perceive not. – Isaiah 6:9

(Israel’s) terrible sin lay in this, that they were willingly blinded by the light which ought to have been to them a help to see Christ, and they were hardened by those very truths which ought to have melted them. They became more and more adverse to Christ through beholding in Him such a character as ought to have won their hearts. To the prophet’s teaching they were entirely dead. A specimen of this we find in the succeeding chapters of Isaiah. Israel and Syria attacked Ahaz, whose reign followed those of Uzziah and Jotham. The prophet came and said to Ahaz, “Take heed, and be quiet; fear not, neither fainthearted for the two tails of these smoking firebrands.” Ahaz was assured that God would help him if he would but trust in Him; but instead of doing so, the king determined to petition for the help of the great king of Assyria, with the result in the long run that “the king of Assyria came unto him and distressed him, but helped him not.” Isaiah, to confirm his message, bade the king choose any sign either in the depth or in the height above; but the infidel king replied, “I will not ask, neither will I test Jehovah.” He had so defiantly cast off allegiance to the true God that he would not even accept a sign, though it was left to his own choice. Thus Isaiah’s message was rejected though put in the most winning form, for the hearts of the people were blinded and hardened so as to choose the way of destruction. Ultimately, as you know, the Assyrians carried the whole people away; for they had rejected God’s message willfully, and wrath came upon them. What a grievous task to be called to preach to such a people!

“Hear the just law, the judgment of the skies!
He that hates truth shall be the dupe of lies.”

~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1844.cfm

And one cried unto another, and said, Holy, holy, holy, is the LORD of hosts: the whole earth is full of His glory…Make the heart of this people fat, and make their ears heavy, and shut their eyes; lest they see with their eyes, and hear with their ears, and understand with their heart, and convert, and be healed. – Isaiah 6:3, 9

Even when men rejected Christ, even when hearts were fat, and eyes were dim, and ears were heavy, even then the whole earth was full of the glory of Christ. When scientists tell us that they cannot see God, I am amazed. To me it is impossible not to see Him. Though I cannot pry with the scalpel into the anatomy of the human frame, yet when I look upon the mere skin of the human countenance I see the handiwork of God. Though I cannot dig into the lower strata of the earth and disentomb the fossil and decipher its stone preserved memorial, yet to me rock, and clay, and sand, and relic of the past, bear the sure hieroglyph of God. Though I cannot inform you of all the interesting details of insect life, or descant upon the secrets of botany, yet to me bees bring honeyed thoughts of God, and flowers breathe the perfume of His love. Where is God? Say rather, Where is He not?

…Alas for the ears which cannot hear when earth, and sea, and heaven, and hell, are all echoing to the tread of the Omnipotent Christ of God. Oh brethren, have you ever seen this vision, have you ever seen God’s glory filling the whole earth?  ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1844.cfm

Above it stood the seraphims: each one had six wings; with twain he covered his face, and with twain he covered his feet, and with twain he did fly. – Isaiah 6:2

In this vision Isaiah saw the flaming spirits that wait upon Christ of God. He calls them “seraphims.” The best interpretation we can give is “burning ones:” they burn in the sense of consuming. They burn up that which ought to be consumed, namely, all kinds of evil. There are powers around our Lord which will destroy evil. You ask me to tell you something about these seraphim; how can I? They have covered their faces, and covered their feet. Since nothing is to be seen, what can I tell you? Neither would it be right for us to speak concerning them, for manifestly it is their desire to be hidden. Who will violate their wish to be concealed? They covered their faces, they covered their feet, and therein they did as good as they say, “Look not on us, but look on Him who sits upon the throne, whose attendants we are.” This much is all we know,-exalted intelligences are in waiting upon our Lord, and are able to fly swiftly at His bidding. Tremble not concerning this error, or that, it shall be burnt up by those agencies which are at the command of our exalted Lord. Spirits from God shall run to and fro, and smite, as with the fire of God, those powers of darkness which now oppress our race. God Himself is a consuming fire: who can dwell with Him but those that are like Him? He maketh His ministers a flame of fire. Around our Lord are the chariots of God, which are twenty thousand, even thousands of angels. His power knows no limit. His word runneth very swiftly; He speaks, and it is done; He commands, and it stands fast. Glory be unto Thee, O Christ! We will not fear nor be discouraged, since these Thy servants are ready to flame forth at Thy bidding. Truly Thou art Jehovah of hosts.~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1844.cfm

In the year that king Uzziah died I saw also the Lord sitting upon a throne, high and lifted up, and His train filled the temple. Isaiah 6:1

Observe that in Isaiah’s vision he not only saw the Lord “upon a throne high and lifted up,” but he saw that “His train filled the temple.” so that in that temple there was room for no one else. The robes of this great King filled all the holy place; and neither priests nor offerers could there find standing room. It is a great thing to see how Jesus fills the heavenly places; in Him dwelleth all the fullness of the Godhead. Let it be acknowledged to be so in heaven, for the glory of our Redeemer fills every street of the upper city, every mansion of the Father’s house. In the church below, which is also His temple, among His spiritual people, the glory of the Lord Jesus engages and occupies every heart. They feel that there is none other in whom they can trust, none other whose words they will receive, none other in whom they glory; the Lord Christ is all in all to us, and we know no other Master or Saviour. His train fills the temple. I trust it is so among us. From Sabbath to Sabbath the one glory of this Tabernacle is the person and work of Jesus. What a glory hath God put upon the Only Begotten Son, whom He hath raised from the dead that He should be head over all things to His church, which He fills with His life, light, and love. Nor may we forget that all the things that exist are in a sense His temple, and the whole universe is filled with His train; for “He hath ascended up far above all heavens that He might fill all things.” Glory be unto our ascended and reigning Lord.~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1844.cfm