Solomon
Ecclesiastes 12:12ESV·traditional attribution

My son, beware of anything beyond these. Of making many books there is no end, and much study is a weariness of the flesh.

Matthew Henry Presbyterian @wholebiblehenry

Solomon is here drawing towards a close, and is loth to part till he has gained his point, and prevailed with his hearers, with his readers, to seek for that satisfaction in God only and in their duty to him which they can never find in the creature. I. He repeats his text (Ecc 12:8), 1.

Commenting on Ecclesiastes 12:8-12

John Gill Reformed Baptist @doctorgill

And further, by these, my son, be admonished,.... Rehoboam, the son of Solomon, may be intended, for whose sake, more especially, this book might be written; though it may take in every hearer of this divine preacher, every disciple of this teacher, every subject of his kingdom, as well as every reader of this book, whom he thus addresses, and for whom he was affectionately...

Jamieson-Fausset-Brown Reformed @jfbcommentary

(See on Ecc 1:18). many books--of mere human composition, opposed to "by these"; these inspired writings are the only sure source of "admonition." (over much) study--in mere human books, wearies the body, without solidly profiting the soul.