Charles H. Spurgeon on Psalms 119:34

Understanding. The understanding is the pilot and guide of the whole man; that faculty which sits at the stern of the soul: but as the most expert guide may mistake in the dark, so may the understanding, when it wants the light of knowledge. "Without knowledge the mind cannot be good" (Proverbs 19:2); nor the life good; nor the external condition safe (Ephesians 4:18). "My people are destroyed for the lack of knowledge" (Hosea 4:6).

It is ordinary in Scripture to set profaneness, and all kinds of miscarriages, upon the score of ignorance. Diseases in the body have many times their rise from distempers in the head;and exorbitance in practice, from errors in the judgment. And, indeed, in every sin, there is something both of ignorance and error at the bottom: for did sinners truly know what they do in sinning, we might say of every sin what the Apostle speaks concerning that great sin, "Had they known him, they would not have crucified the Lord of glory" (1 Corinthians 2:8). Did they truly know that every sin is a provoking the Lord to jealousy, a proclaiming war against heaven, a crucifying the Lord Jesus afresh, a treasuring up wrath afresh unto themselves against the day of wrath; and that if ever they be pardoned, it must be at no lower a rate than the price of his blood it were scarce possible but sin, instead of alluring, should affright, and instead of tempting, scare. From the "Recommendatory Epistle prefixed to the Westminster Confession and Catechisms."