The gospel necessarily comes with an urgent warning, because the distinction between those who obey its call and those who disobey is not merely between a better life and a worse life. It is the difference between life and death. It is an eternal distinction, for the cost of disobedience and the cost of not hearing the gospel is eternal death.
That is why we must preach with the urgency of a dying man. It is because human beings are in desperate need of salvation. Time is short, God's wrath is certain, and eternity hangs in the balance. Moreover, there is for each of us only one way out of this predicament, and that is the salvation God Himself has won through the gospel of His Son, Jesus Christ.
Albert Mohler, He is Not Silent
The Supremacy of God in Preaching by John Piper
Expositional Preaching: How We Speak God's Word Today by David R. Helm
Preaching: A Biblical Theology by Jason Meyer
Preaching and Preachers by Martyn Lloyd-Jones
Preach: Theology Meets Practice by Greg Gilbert and Mark Dever