Now go and strike Amalek, and utterly destroy all that they have, and don't spare them; but kill both man and woman, infant and suckling, ox and sheep, camel and donkey.
Now he has shown a pattern of disobedience up to this point. He has become self-willed, doing his own thing. So the prophet is coming and warning him. This to me is very significant, because God does seek to warn us from our self-willed path of destruction. God doesn't just let you trip off into the path of destruction, without coming and giving you fair warning, oftentimes, repeated warnings.