Prov 8:9

“[Jesus] "spoke all things in parables, and without a parable he spoke nothing" [to the apostles]; and if "all things were made by him, and without him was not anything made that was made," consequently also prophecy and the law were by him and were spoken by him in parables. "But all things are right," says the Scripture, "before those who understand," that is, those who receive and observe, according to the church's rule of faith, the exposition of the Scriptures explained by him. And the church's rule is the concord and harmony of the law and the prophets in the covenant delivered at the coming of the Lord. Knowledge is then followed by practical wisdom and practical wisdom by self-control, for it may be said that practical wisdom is divine knowledge and exists in those who share in God's life, while the self-control that is mortal, which is present in those who philosophize, is not yet wise.”

“They are all plain to him that understandeth,.... Whose understanding is enlightened by the Spirit of God; who is a spiritual man, that has a discerning, and can judge of spiritual things: as for the carnal man, let him have what natural knowledge or wisdom he will, he cannot know these things; for they are spiritually discerned, and can only be discerned by spiritual men. The Bible is a sealed book to others, learned or unlearned; the mysteries or doctrines of the Gospel are hid in parables from such; but those to whom Christ has given an understanding to know him, these know them, and they are plain unto them: for though there are some things hard to he understood in the Scriptures, as in Paul's epistles, and some sublime truths in the Gospel; yet those which are necessary to salvation are easily understood; that faithful saying, and worthy of all acceptation, that Jesus Christ came into the world to save the chief of sinners, is a very plain one; and right to them that find knowledge; a spiritual and experimental knowledge of Christ and his truths. The Targum is, "to them who desire knowledge;'' and so the Syriac version; that seek for it heartily and diligently, in a right way, in the use of proper means, under the direction and by the assistance of the Spirit of God.”