Proverbs 26:7, 9 Poor preaching useless and dangerous

Like the useless legs of one who is lame is a proverb in the mouth of a fool. ... Like a thornbush in a drunkard’s hand is a proverb in the mouth of a fool.

It is not enough to know proverbs in order to be wise. You need to know how to apply the proverbs found in the Book of Proverbs. Similarly, it is not enough to know Scripture in order to be a good preacher. You need to know how to preach Scripture. There is a school of thought that says that preaching is just a matter of telling them what the Bible says. It is akin to the idea that simply reading oriverbs will make a person wise. No, there is more to it than that. And so just as a fool quoting a  proverb can be as useless as a man who is lame and as dangerous as a drunkard with a thornbush (wath out!) so those who know their Bibles but can't preach are both useless and dangerous.

Talking about the Puritans Dr Lloyd-Jones says

What was it that turned the world upside down? Was it just theological teaching? Was it mere enunciation of correct doctrine? Over and above that there was this mighty ‘demonstration of the Spirit and of power.’ How did those people turn the world upside down? The answer is that in the Book of Acts we have an account of a great revival, of the Spirit outpoured. What happened could not have happened otherwise. How did all these churches come into being? Was it merely that the apostles taught correct doctrine? Of course not! It was the Spirit’s demonstration and power which accompanied the correct doctrine. Correct doctrine can leave the church dead; you can have dead orthodoxy, you can have a church that is perfectly orthodox but perfectly useless. Over and above, there was this demonstration, this unction, this authority, this outpouring of the Spirit’s power. It is the only explanation of the astonishing things that happened.