Now the name of the man was Nabal; and the name of his wife Abigail; and the woman was of good understanding, and of a beautiful face: but the man was churlish and evil in his doings; and he was of the house of Caleb.
"He was a Calebite" The Calebites were attached to the tribe of Judah; and since Judah would be the tribe most loyal to David, it was extremely important that David should have been rescued in this chapter from his temptation to slaughter Nabal and all his house.  If David had indeed done such a thing, it could have alienated the whole tribe of Judah. The big thing in this chapter is the manner in which God saved David from that terrible mistake.