What does Isaiah 10:20 mean?
The chapter continues to move between descriptions of God's judgment on His people Israel and His mercy. On the one hand, the Lord will soon make use of the Assyrians to bring terrible judgment upon Israel and Judah. On the other hand, the Lord will not wipe His people out. He will preserve a remnant. And those left will finally trust in Him to take care of them.There are two events, then in the future when Isaiah wrote, to which he may be referring. In 701 BC, the Assyrians will have Jerusalem in a siege. Things will look hopeless for the survivors of the Lord's people locked inside the gates of the City of David. The Lord will save them. by sending the angel of the Lord to strike 185,000 Assyrians dead in one night (2 Kings 19:35). Much later, a remnant of God's people will return to Jerusalem from captivity in Babylon.
Isaiah writes that the house of Jacob will no longer rely on the one who "struck them." He may be referring to the fact that King Ahaz attempted to make an alliance with Assyria to find safety from his other enemies (2 Kings 16:7–10). Hosea describes Ephraim's foolishness in trying to rely on foreign nations, like Egypt and Assyria, to protect Israel instead of the Lord (Hosea 7:11).
The other possible event in mind may be the return of Israel from exile, as described in the books of Ezra and Nehemiah. A further event, future to both Isaiah and ourselves, is when the remnant of Israel will once again lean on the Holy One of Israel. This is a reference to the end times. Though few will remain in this time, God's people will once more trust Him and Him alone. Isaiah adds the words "in truth" to show that this trust in the Lord will not be meaningless ritual, but true faith.