Behold, thou desirest truth in the inward parts
With delight and pleasure, as the word F4 signifies: meaning either Christ, the truth and the life, formed and dwelling in the hearts of his people; or the Gospel, the word of truth, which has a place there; and particularly that branch of it which proclaims pardon to sensible sinners, and is the ground of hope within them: or else a true and hearty confession of sin, which David now made; or rather internal holiness and purity of heart, in opposition to the corruption of nature before acknowledged: this is what is agreeable to the nature of God, is required by his holy law, and is wrought in the hearts of his people in regeneration; and this is "truth", real, and not imaginary, genuine and unfeigned; where it is there is a true sense of sin, a right sight of Christ, unfeigned faith in him, sincere love to him, hope in him without hypocrisy, and a reverential fear of God upon the heart; the inward parts are the seat of all this, and in the exercise of it the Lord takes great delight and pleasure;
and in the hidden [part] thou shall make me to know wisdom;
either Christ, the wisdom of God; or the Gospel, and particularly that part of it which concerns the pardon of sin; or a true knowledge of sin, and of the way of life and salvation by Christ, which is the truest and highest wisdom: and the phrase "hidden" or "secret" may either denote the nature of the wisdom made known, which is hidden wisdom, the wisdom of God in a mystery; or the manner in which it is made known; it is in a hidden way, privately, and secretly, and indiscernibly like the wind, by the Spirit and grace of God; or the seat and subject of it, "the hidden part", as we supply it; the hidden man of the heart. David begins to rise in the exercise of his faith in the grace of God, "thou shall make me to know" unless the words should be rendered as a prayer, as they are by some, "make me to know" F5 and as are the following.
F4 (tupx) "delectaris", Junius & Tremellius, Piscator; "delectatus es", Cocceius; so Ainsworth.
F5 (yneydwt) "notam mihi fac", Gejerus.