Psalm 51:7
And in the hidden part - In the secret part; the heart; the depths of the soul. The cleansing was to begin in that which was hidden from the eye of man; in the soul itself. Wisdom, heavenly, saving wisdom, was to have its seat there; the cleansing needed was not any mere outward purification, it was the purification of the soul itself.
Thou shalt make me to know wisdom - Thou only canst enable me to understand what is truly wise. This wisdom, this cleansing, this knowledge of the way in which a guilty man can be restored to favor, can be imparted only by thee; and “thou wilt do it.” There is here, therefore, at the same time a recognition of the truth that this “must” come from God, and an act of faith, or a strong assurance that he “would” impart this.