David said, As Yahweh lives, Yahweh will strike him; or his day shall come to die; or he shall go down into battle and perish.
So David is sort of chiding Abner the chief general of Saul, saying, "Hey you know your job is to guard the king, and you aren't doing a good job. You ought to be put to death. Someone came in to destroy the king, and you were just sound asleep. Look where the king's spear is, and the cruse of water."