Joel 3:17

Shall ye know. Because of the misfortunes that had befallen the Jewish nation, many had been led to question the merciful purposes of God. But the Lord declared that He would show forth His mighty power in the deliverance of His people. Thus His character and beneficent design would be fully vindicated before the inhabitants of earth (see on Eze. 6:7; 38:23; cf. Eze. 39:22, 28).

Pass through her. That is, with evil designs. Strangers who had joined themselves to the Lord were, of course, welcome (Isa. 56:6). God’s design was that with regularity “all flesh” would come to worship before Him (Isa. 66:23).

The picture is of the Jerusalem that might have been (see on Isa. 65:17). When the New Jerusalem comes down from God out of heaven (Rev. 21:2), Satan and the vast host with him will seek to overrun the Holy City, but they will perish in the attempt (Rev. 20:9).