Thus says Yahweh of Hosts, I have marked that which Amalek did to Israel, how he set himself against him in the way, when he came up out of Egypt.
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.