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

 - Greek mythology
 - the Bible
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.