John Gill's Bible Commentary
Ver. 20. Have not I written to thee excellent things , etc.] In the Scriptures. Some render it, “three things” f606 ; and think that Solomon refers to the three divisions of the Scriptures among the Jews, the law, the prophets, and holy writings; so Jarchi; but some of those writings then were not: or to the three books wrote by him; the Proverbs, Ecclesiastes, and Song of Songs. Others render it, “in a threefold way” f607 , as the Targum and several versions; that is, in various ways, in different forms and styles, in order the better to inform and instruct. But it is best, with Kimchi, Gersom, and Ben Melech, to render it, “excellent things”, as we do; such are the truths of the Gospel; they are more excellent than those that are only known by the light of nature, or by the law of Moses: such as suspect the love and grace of God; the person and offices of Christ; peace, pardon, righteousness, atonement, life and salvation, by him. And these are said to lie in counsels and knowledge ; in disclosing the counsels of God, according to which they are; in giving the best of counsels to men; to perishing sinners, to look to Christ for salvation; to naked ones, to buy of him white raiment, or the robe of his righteousness; to guilty and filthy ones, to apply to his blood for pardon and cleansing; to hungry and thirsty ones, to come unto him for food, the bread of life, and water of life; and to weary ones, to him for rest; and all to do their duty both to God and men: and they also respect knowledge; the knowledge of divine and heavenly things; the knowledge of God in Christ, and of his perfections, as displayed in his salvation; the knowledge of Christ, what he is in himself, what he has done for his people, and is unto them; and especially the knowledge of salvation by him; all which the Gospel is a means of.
Matthew Henry Commentary
Verses 17-21 - To these words, to this knowledge, the ear must be bowed down, and the heart applied by faith and love. To live a life of delight in God an dependence on him, is the foundation of all practical religion. The way to know the certainty of the word of truth, is to make conscience of our duty.
Original Hebrew
הלא 3808 כתבתי 3789 לך שׁלשׁום 8032 במעצות 4156 ודעת׃ 1847