Albert Barnes Commentary Deuteronomy 29:4

"but Jehovah hath not given you a heart to know, and eyes to see, and ears to hear, unto this day." — Deuteronomy 29:4 (ASV)

Ability to understand the things of God is the gift of God (compare 1 Corinthians 2:13–14); yet man is not guiltless if he lacks that ability. The people did not have it because they had not felt their need of it, nor asked for it. Compare 2 Corinthians 3:14–15.