Solomon
Ecclesiastes 1:18ESV·traditional attribution

For in much wisdom is much vexation, and he who increases knowledge increases sorrow.

Matthew Henry Presbyterian @wholebiblehenry

Solomon, having asserted in general that all is vanity, and having given some general proofs of it, now takes the most effectual method to evince the truth of it, 1. By his own experience; he tried them all, and found them vanity. 2.

Commenting on Ecclesiastes 1:12-18

John Gill Reformed Baptist @doctorgill

For in much wisdom is much grief,.... In getting it, and losing it when it is gotten: or "indignation" (t), at himself and others; being more sensible of the follies and weakness of human nature; and he that increaseth knowledge increaseth sorrow: for, the more he knows, the more he would know, and is more eager after it, and puts himself to more pains and...

Jamieson-Fausset-Brown Reformed @jfbcommentary

wisdom . . . knowledge--not in general, for wisdom, &c., are most excellent in their place; but speculative knowledge of man's ways (Ecc 1:13, Ecc 1:17), which, the farther it goes, gives one the more pain to find how "crooked" and "wanting" they are (Ecc 1:15; Ecc 12:12).