Hosea 7:9

Strangers have devoured. This mixture of Israel with the heathen (v. 8) could result in nothing but trouble. Idolatrous foreign nations did devour Ephraim’s strength. Syria reduced the armed forces of Jehoahaz to a humiliatingly small number (2 Kings 13:3-7). Menahem had to pay tribute to Assyria (2 Kings 15:17-20). In the reign of Pekah, Tiglath-pileser, king of Assyria, took Israelitish territory and carried the people captive to Assyria (2 Kings 15:29; 1 Chron. 5:26). All this took place before the kingdom ended with the fall of Samaria (2 Kings 17:5-18).

Gray hairs. A symbolic representation of Israel’s declining national strength and the decay of her national importance.

Yet he knoweth not. This does not necessarily mean that Israel did not know she was in a decadent, failing condition. The facts within and without the nation were too evident. What they did not discern was that this decline was due to their apostasy. Israel was without the essential knowledge that should have been (see on ch. 4:6).