(Isaiah 55:10-11) “For as the rain comes down, and the snow from heaven, And do not return there, But water the earth, And make it bring forth and bud, That it may give seed to the sower And bread to the eater,
11 So shall My word be that goes forth from My mouth; It shall not return to Me void, But it shall accomplish what I please, And it shall prosper in the thing for which I sent it.
People tend to take this passage to mean that whenever God's word is proclaimed it will accomplish God's purpose in the people who hear it. But keep in mind that in the context, "my word" means the things God has said will happen for the purification and restoration of Israel according to Isaiah's prophecy. What it means is that what God says He will accomplish, will indeed be accomplished in due time.
God is infinite, omniscient and omnipotent. He is sovereign and He will do His will according to His plan and His pleasure. So what does this mean about our proclamation of the word of God? He says,
(2Timothy 4:2-4) Preach the word! Be ready in season and out of season. Convince, rebuke, exhort, with all longsuffering and teaching.
3 For the time will come when they will not endure sound doctrine, but according to their own desires, because they have itching ears, they will heap up for themselves teachers;
4 and they will turn their ears away from the truth, and be turned aside to fables.
So, in fact, we are to preach God's word with the full realization that many of our hearers will reject it and turn from the truth to fables.
This should not discourage us from the preaching of God's word. God is still infinite, omniscient and omnipotent. While we do not want to misapply Isaiah 55:10-11, we still know that God will indeed accomplish His perfect will through the preaching of His word.
(1Corinthians 1:21) For since, in the wisdom of God, the world through wisdom did not know God, it pleased God through the foolishness of the message preached to save those who believe.
As we preach God's word in the gospel of Jesus Christ, God works to bring people to salvation. Apart from proclaiming God's word, people will not be saved.
(Romans 10:14) How then shall they call on Him in whom they have not believed? And how shall they believe in Him of whom they have not heard? And how shall they hear without a preacher?
Our sovereign God will accomplish His purposes and He is pleased to use the preaching of His word for His purposes of salvation. But it isn't automatic or magic. It is our infinite and transcendent God personally working in our fallen and finite world to bring salvation to the rebels by His sovereign grace.