John Gill Commentary Isaiah 17:3

"And the fortress shall cease from Ephraim, and the kingdom from Damascus, and the remnant of Syria; they shall be as the glory of the children of Israel, saith Jehovah of hosts." — Isaiah 17:3 (ASV)

The fortress also will cease from Ephraim. The ten tribes, now in confederacy with the Syrians, whose metropolis or fortress was Samaria. This seems to be intended here, and it would be destroyed, at least taken out of the hands of the Israelites, and they would be carried captive by Shalmaneser king of Assyria (2 Kings 17:6). This may be understood, not of that particular city and fortress only, but of all their strongholds, the singular being put for the plural. The Targum is, "the government will cease from Ephraim"; they will have no more a king over them, nor have they to this day.

And the kingdom from Damascus, and the remnant of Syria. Damascus was the head city of Syria, where the kings of Syria had their palace; but now that and the rest of Syria would no longer be a kingdom of itself, but would be subject unto others, as it has been ever since.

They shall be as the glory of the children of Israel, says the Lord of hosts. That is, the Syrians, who were in alliance with Israel, would share the same fate. They would be carried captive as they were, have their metropolis and other cities, and their whole kingdom, taken from them, and be stripped of their grandeur and wealth. They would have no more glory than they had, which was none at all, or at least very small, as the next verse shows (Isaiah 17:4).