Albert Barnes Commentary Isaiah 7:17

"Jehovah will bring upon thee, and upon thy people, and upon thy father`s house, days that have not come, from the day that Ephraim departed from Judah-[even] the king of Assyria." — Isaiah 7:17 (ASV)

The Lord shall bring ... - The prophet, having assured Ahaz that his kingdom would be free from the invasion that then threatened it, proceeds, however, to state to him that it would be endangered from another source.

Thy father’s house - The royal family - the princes and nobles.

Days that have not come - Times of calamity that have not been equalled.

From the day that Ephraim departed from Judah - From the time of the separation of the ten tribes from the tribes of Judah and Benjamin.

Even the king of Assyria - This occurred in the following manner. Although the siege undertaken by Rezin and Pekah was not successful at this time, they returned the following year with stronger forces and better-concerted plans, and besieged the city again. This was a consequence of the continued and increasing wickedness of Ahaz (2 Chronicles 28:1–5).

In this expedition, a great multitude were taken captive and carried to Damascus (2 Chronicles 28:5). Pekah also killed 120,000 of the Jews in one day at this time (2 Chronicles 28:6), and Zichri, a valiant man of Ephraim, killed Maaseiah, the son of Ahaz. Furthermore, Pekah took no less than 200,000 people from the kingdom of Judah, intending to take them to Samaria, but was prevented by the influence of the prophet Oded (2 Chronicles 28:8–15).

In this calamity, Ahaz stripped the temple of its treasures and ornaments and sent them to Tiglath-pileser, king of Assyria, to persuade him to come and defend him from the combined forces of Syria and Ephraim.

The consequence was, as might have been foreseen, that the king of Assyria took this as an opportunity to bring increasing calamities upon the kingdom of Ahaz. Indeed, he first killed Rezin and took Damascus (2 Kings 16:7).

Having subdued the kingdoms of Damascus and Ephraim, Tiglath-pileser became a more formidable enemy to Ahaz than both of them combined. His objective was not to aid Ahaz, but to distress him (2 Chronicles 28:20). Indeed, his coming—professedly to help and at Ahaz's request—was a more formidable calamity than the threatened invasion by both Rezin and Pekah.

God has the power to punish a wicked nation in His own way. When people seek human aid, He can turn this very aid into a scourge. He has kings and nations under His control. Even if a wicked prince seeks an earthly alliance, it is easy for God to allow such allies to indulge their ambition and love of plunder, making them the very instruments for punishing the nation they were called to defend.

It should be observed that this phrase, ‘even the king of Assyria,’ is thought by many critics to be spurious, or a marginal reading or gloss that has, by some means, crept into the text.

The ground of this opinion is that the phrase does not entirely harmonize with the following verse, where Egypt is mentioned as well as Assyria, and that it does not agree with the poetical form of the passage.