David asked Saul whom he was pursuing: "A dead dog? A…" what?

Answer: Flea

After sparing Saul in the cave, David humbly compared himself to a dead dog and a flea, insisting he meant Saul no harm.

“Against whom has the king of Israel come out? Whom are you pursuing? A dead dog? A flea?”— 1 Samuel 24:14 (BSB)