Problem: The NT writers quote the vast majority of the OT from Genesis to Malachi. There are literally hundreds of citations from every major section of the OT. Yet, the Book of Ecclesiastes is not quoted once. If it was inspired, then why isn’t it cited at least one time?
Solution: There are several OT books that are not directly quoted in the NT, including Ruth, 1 and 2 Chronicles, Esther, Song of Solomon, and Ecclesiastes. However, all these books were considered inspired by both Judaism and Christianity. Several points should be kept in mind.
First, being quoted in the NT was not a test for the inspiration of an OT book. Rather, the question was whether it was written by a spokesperson accredited by God and accepted by His people. Ecclesiastes meets this test.
Second, while no text of Ecclesiastes is cited as such in the NT, many of its truths are. For example:
Third, the NT writers had no occasion to quote from every book in the OT. Few Christians have quoted recently from 1 Kings, yet the NT did (Rom. 11:4). Indeed, few believers ever cite 2 or 3 John, and yet they are part of the inspired Word of God. Whether, or even how often, a book is quoted does not determine whether it is inspired.