Adam Clarke on Hosea 5:13

When Ephraim saw his sickness - When both Israel and Judah felt their own weakness to resist their enemies, instead of calling upon and trusting in me, they sought sinful alliances, and trusted in their idols.

King Jareb - This name occurs nowhere in Scripture but here and in Hos 10:6. The Vulgate and Targum render ירב yareb, an avenger, a person whom they thought able to save them from their enemies. It is well known that Menahem, king of Israel, sought alliance with Pul and Tiglath-pileser, kings of Assyria, and Ahaz, king of Judah. These were the protectors that Ephraim sought after. See 2 Kings 15 and 16. But far from healing them by making them tributary, the Assyrians made their wound more dangerous.