The fool hath said in his heart, There is no God. They are corrupt, they have done abominable works, there is none that doeth good. (Psalms 14:1)

In the 14th Psalm, in the first verse, we read of a “fool” (spelled nabal) who said in his heart “there is no God” — how stupid can you get?! The verse goes on to recount how such a fool is “corrupt” and is known for doing “abominable deeds”.
Is it a stretch to assume that the psalmist David was remembering, as a “poster child” example of such a “fool”, the very fool named “Nabal” (which means fool in Hebrew) whose downfall and death are recorded in 1st Samuel chapter 25? Even Abigail, his wife (who knew him well), said of Nabal, “Let not my lord … regard this son of Belial, even Nabal: for as his name is, so is he; Nabal is his name, and folly is with him.”
Also, interestingly, that same chapter (i.e., 1st Samuel 25) exhibits David himself as a hot-headed impetuous fool, yet moreso as a temper-suppressing teachable fool, who timely pulls back from carrying out intended revenge-killings, after being providentially reminded of God and God’s morality.
In viewing the theology of a “fool” (Hebrew nabal: לבנ), see Romans 3:12, quoting Psalm 14:1; notice also that Psalm 53:1 reiterates most of Psalm 14:1. (See also Psalm 10:4-13.) The Lord told of a foolish man who planned to build bigger barns for his worldly wealth, but his worldly plans were interrupted by a sudden death (Luke 12:15–21, 12:34)!
Insane exhibitions of flabbergasting follies are ubiquitous nowadays, illustrating the obvious truth, taught by the Lord Jesus Himself, which compares living life to building a house upon a foundation, “And every one who hears these sayings of Mine, and doeth them not, shall be likened unto a foolish man, who built his house upon the sand….” (Matthew 7:26).
“The fear [which “fear” includes a humble reverence and respect for God being God Almighty] of the LORD is the beginning of knowledge; but fools despise wisdom and instruction (Proverbs 1:7).
Arrogant “modern” humans, while they profess their own intelligence and education, close the Holy Bible — as they reject its truths and its divine Author. How foolish! “Because that, when they knew God, they glorified Him not as God; neither were they thankful; but they became vain [i.e., empty-minded] in their imaginations, and their foolish heart was darkened” (Romans 1:21).
Don’t be a “Nabal”. Revere God and be teachable!
