Two talmudic passages suggest that ancient rabbinic authorities considered removing the book of Ecclesiastes from the canon, and the standard midrashic commentary on the book states outright that some of its ideas “lean toward heresy.” While medieval exegetes found ways to harmonize the book with accepted doctrines, one brilliant and idiosyncratic Italian rabbi simply threw up his hands. Martin Lockshin writes:
Samuel David Luzzatto (Shadal; 1800–1865) was a prolific poet, thinker, linguist, and scholar who composed Bible commentaries that, while rejecting most of the teachings of 19th-century biblical criticism, had a decidedly modern flavor. Most of his life, he taught Bible in the modern, Orthodox rabbinical seminary in Padua.
When he was twenty years old, he wrote a commentary on Ecclesiastes which he did not publish. . . . Luzzatto [therein] argues that Ecclesiastes rejects divine personal providence and feels that what happens to people is a result of fate. . . . Luzzatto opposes the final decision of the classical rabbis to include Ecclesiastes in the canon, and he supports the earlier rabbis at the beginning of the first millennium, who, according to classical rabbinic literature, wanted to exclude Ecclesiastes from the Bible.
Thirty-six years later, a mature Luzzatto sent the manuscript to a publisher, with a note explaining that his views of the book had changed, and that he had a newfound appreciation for it. To some extent Luzzatto’s new view mirrors the traditional understanding that King Solomon wrote the Song of Songs in his youth and Ecclesiastes in his old age. Luzzatto wrote:
I hereby apologize and ask forgiveness from the author of Ecclesiastes (whoever he may be). For in the days of my youth . . . I was angry at [him] for saying “Vanity of vanities, all is vanity. What benefit do people receive from all their efforts?” (1:2–3). . . . Of all the many books that I have seen and read, very few were as valuable to me as the book of Ecclesiastes. . . . From it, I derived the approach that guides me to this very day, that for people whose lives are dedicated to their own benefit, they are vanity and their existence is vanity. But people whose lives and efforts are dedicated to helping others, their lives are not vanity.
Read more on theTorah.com: https://www.thetorah.com/article/is-kohelets-wisdom-vanity-of-vanities