What is the source of the allusion in the sentence below?
Yesterday's tennis match was a classic David and Goliath story, with Jayce playing against his former team captain, Tamir.

 - the Bible
 - a poem
The source of the allusion David and Goliath is the Bible.
In the Bible, a young man named David slays Goliath, a giant and champion warrior, using nothing more than a sling and a stone.
The allusion David and Goliath means involving unequal rivals.