What did the Lord command Isaiah to do to make the heart of this people fat, their ears heavy, which caused them to close their eyes? Isaiah was to simply preach Christ Jesus the Lord, the Son of God, the Messiah, the Holy One of Israel. Most delighted to participate in hearing the message preached. They drew near to the Lord, or at least appeared to (Isa 29: 13, 14; Isa 30: 8-11.)

Yet, in hearing Isaiah's gospel the Lord declared he would make the heart of this people fat (v10.) Literally, their hearts swelled with pride as they thought themselves secure because of their act of seeing and hearing. But like the sun hardens the clay, so God's Word hardened their hearts. Their ears became heavy (v10) because as they refused to hear, they became more deaf so that they could not hear. They shut their eyes (v10) and because they willfully shut their own eyes to the truth of the Messiah, God gave them up to judicial blindness. So that they could not see with their eyes, and hear with their ears, and understand with their heart, and convert, and be healed (2 Thes 2: 10-12.)

The declaration is clear. Until God gives the sinners a new heart, spiritual discernment and a willingness to come to Christ then our religion is vanity. Listen to the words of Christ Jesus to the religious elite who mocked him. John 9: 39: And Jesus said, For judgment I am come into this world, that they which see not, might see; and that they which see, might be made blind. 40: And some of the Pharisees which were with him heard these words, and said unto him, Are we blind also? 41: Jesus said unto them, If ye were blind, ye should have no sin: but now ye say, We see; therefore your sin remaineth.

Hear the word of the Lord, "If ye were blind, if you cried out to God for sight, not only would you have sight, you should have no sin." But now you say, "I see, therefore your sin remaineth." Unless a man be born of God he cannot see...(Joh 3: 3.) This truth will make a blind man mock even more. But it will make one in whom God has given sight to say, "Who is Christ, Lord, that I might believe on him?" And that man shall hear Christ in the heart saying, "Thou hast both seen him, and it is he that talketh with thee." (Joh 9: 34-38.)