Charles Ellicott Commentary 1 Samuel 25:10

"And Nabal answered David`s servants, and said, Who is David? and who is the son of Jesse? there are many servants now-a-days that break away every man from his master." — 1 Samuel 25:10 (ASV)

There are many servants nowadays who break away. —This evident insult indicates that Nabal was of Saul's faction at this time—was counted among those who hated David. It was the report of these words, undoubtedly, that so furiously provoked David. In Nabal, the rich sheep owner, the boorish refuser of the fairly earned gift, David saw a deadly political adversary—one who, with men like Doeg and Cush, would hunt him down like a wild beast.

Without this explanation, David’s wrath and determination to take such speedy and bloody vengeance on a mere selfish boor are inexplicable. However, with the light that such an open declaration of deadly hostility on Nabal's part throws on the transaction, David's subsequent passionate conduct, although deeply blameworthy, is not difficult to understand.