19. Wherefore? The thought returns to the main theme of the chapter: the causes of the judgments about to come upon the nation. In case the Jews should be insolent enough to ask the reasons for the calamities in view of God’s promises to them and His choice of them as His special people, the prophet was to reply with a countercharge: Judah had forsaken the Lord and had turned to idolatry. God’s promises had been given on condition of obedience and loyalty.
In chariots. Here are listed the various types of transportation in use in the ancient East. By every available means men from every race and clime would make their way to Zion.
So shall ye serve. The punishment was adapted to meet the nature of the offense. God had given them His land, but since they preferred to serve foreign deities, they would be carried away to serve foreigners in a foreign land (see Deut. 28:47, 48).
My holy mountain Jerusalem. See on 2:2-4.