And moreover, because the preacher was wise, he still taught the people knowledge; yea, he gave good heed, and sought out, and set in order many proverbs.

Wesley's Notes

12:9 Taught - As God gave him this wisdom, that he might be a teacher of others. So he used it to that end. Gave heed - He did not utter whatever came into his mind, but seriously pondered both his matter and words.

King James Translators' Notes

moreover...: or, the more wise the preacher was, etc

Jamieson-Fausset-Brown Bible Commentary

9. gave good heed-literally, "he weighed." The "teaching the people" seems to have been oral; the "proverbs," in writing. There must then have been auditories assembled to hear the inspired wisdom of the Preacher. See the explanation of Koheleth in the [669]Introduction, and [670]chapter 1 (1Ki 4:34).

that which is written, &c.-rather, (he sought) "to write down uprightly (or, 'aright') words of truth" [Holden and Weiss]. "Acceptable" means an agreeable style; "uprightly . truth," correct sentiment.

Matthew Henry's Concise Commentary

12:8-14 Solomon repeats his text, VANITY OF VANITIES, ALL IS VANITY. These are the words of one that could speak by dear-bought experience of the vanity of the world, which can do nothing to ease men of the burden of sin. As he considered the worth of souls, he gave good heed to what he spake and wrote; words of truth will always be acceptable words. The truths of God are as goads to such as are dull and draw back, and nails to such as are wandering and draw aside; means to establish the heart, that we may never sit loose to our duty, nor be taken from it. The Shepherd of Israel is the Giver of inspired wisdom. Teachers and guides all receive their communications from him. The title is applied in Scripture to the Lord Jesus Christ, the Son of God. The prophets sought diligently, what, or what manner of time, the Spirit of Christ in them did signify, when it testified beforehand the sufferings of Christ, and the glory that should follow. To write many books was not suited to the shortness of human life, and would be weariness to the writer, and to the reader; and then was much more so to both than it is now. All things would be vanity and vexation, except they led to this conclusion, That to fear God, and keep his commandments, is the whole of man. The fear of God includes in it all the affections of the soul towards him, which are produced by the Holy Spirit. There may be terror where there is no love, nay, where there is hatred. But this is different from the gracious fear of God, as the feelings of an affectionate child. The fear of God, is often put for the whole of true religion in the heart, and includes its practical results in the life. Let us attend to the one thing needful, and now come to him as a merciful Saviour, who will soon come as an almighty Judge, when he will bring to light the things of darkness, and manifest the counsels of all hearts. Why does God record in his word, that ALL IS VANITY, but to keep us from deceiving ourselves to our ruin? He makes our duty to be our interest. May it be graven in all our hearts. Fear God, and keep his commandments, for this is all that concerns man.