John Chrysostom

Hear what Solomon says, who knew the present world by actual experience. "I builded me houses, I planted me vineyards, I made me gardens, and orchards and pools of water. I gathered me also silver and gold. I gat myself men-singers, and women-singers, and flocks, and herds." There was no one who lived in greater luxury, or higher glory. There was no one so wise or so powerful, no one who saw all things so succeeding to his heart's desire. What then? He had no enjoyment from all these things. What after all does he say of it himself? …

Homilies On 1 Timothy 15 ↗

Jerome

"Vanity of vanities says Ecclesiastes; all is vanity." Then after the description of man's death, he goes back to the beginning of his book, saying, "vanity of vanities, says Ecclesiastes, all is vanity" [Eccl. 1,2.]. For all toil of mortal men, which is argued all through the books, is pertinent here, so that dust returns to the earth, and the spirit returns to the place, whence it was taken, it is a great vanity in this world to toil and obtain nothing for the future from it.

Commentary on Ecclesiastes ↗

Bonaventure

As was said from the beginning of the book, this entire book has an order directed toward proving one proposition, which he set forth at the beginning of the book, namely this: "Vanity of vanities" etc. This he proved throughout the entire book and now at the end concludes, saying: "Vanity of vanities, said Ecclesiastes." Above he similarly said, that is, proposed: but now: "Ecclesiastes said," that is, concluded. …

Commentary on Ecclesiastes, Chapter 12 ↗