In this section the prophet, as if despairing of any improvement or amendment on the part of Israel, still resolutely bent on spiritual whoredom, addresses an earnest warning to Judah. From proximity to those idolatries and debaucheries so prevalent in this northern kingdom, and from the corruption at least of the court in the southern kingdom during the reigns of Joram, Ahaziah, and Ahaz, Judah was in danger; and hence the prophet turned aside, with words of earnest warning, to the sister kingdom not to involve herself in the same or similar guilt.
Rashi's brief comment here is, "Let not the children of Judah learn their ways."