The proper selection of a text is a matter of major significance. Good sermon preparation requires taking a passage of Scripture and analyzing it, organizing it, illustrating it, and then applying it to everyday living. The text is to be understood, believed, and applied to both personal and social needs.
Yes, it must always be a biblical text. That text may originate from Bible reading, from a series I am preaching, or from a perceived human need. When a pastor prepares a sermon, he must, in reality, or through his creative imagination, focus upon human needs, hurts, and failures.
I enjoy preaching a thematic series of messages based on the perceived needs of the congregation. If I am aware of a particular need, I will look for a text that would help me explain that particular need.
More often, though, the text is a paragraph out of an extended passage of Scripture that I am preaching through. The text commonly emerges from the series that I am preaching, and the series generally comes from a book of the Bible.
As a general rule, for exegetical preaching, a paragraph should constitute three or four verses of Scripture.
*This question and answer were extracted from "Love Worth Finding: The Life of Adrian Rogers and His Philosophy of Preaching.”