Isaiah 17:9

"In that day shall their strong cities be as the forsaken places in the wood, and on the mountain top, which were forsaken from before the children of Israel; and it shall be desolate. For thou has forsaken the God of thy salvation, and hast not been mindful of the Rock of thy strength; therefore thou plantest pleasant plants, and settest it with strange slips. In the day of thy planting thou hedgest it in, and in the morning thou makest thy seed to blossom; but the harvest fleeth away in the day of grief and of desperate sorrow."

What could more logically have been given a place at this point in the prophecy? It had just been pointed out that Ephraim had adopted the idolatrous religion of the pagans. Very well! God here explained what that really meant for his rebellious children. First (in Isaiah 17:9) he pointed out that those very groves and hill-tops where the pagan altars were located were absolutely deserted by their worshippers, the pagan gods and goddesses the people adored being totally helpless to stand before the conquering armies of Joshua. Ephraim would not learn from that experience; so here God said, "It shall happen again!" Just as the pagan gods could not help those who were driven out of Palestine to make room for Israel will also be unable to do anything to help the Israelites who have foolishly taken up their false worship. The text bluntly stated it: "And it SHALL BE desolate." Then, when Israel came into Canaan, it WAS desolate. Now that Israel has adopted paganism, it SHALL be desolate.

"The sense here is that Israel shall be punished with a desolation like that which the former inhabitants experienced at the hands of the Israelites."[9] Furthermore those pagan gods and goddesses the Israelites have adopted will be able to help Israel no more than they could help those former peoples who lived in Canaan. The forsaking of God and the planting of pleasant plants with strange slips, "Are allegorical expressions for the Israelites' adoption of strange and idolatrous worship and of the vicious and abominable practices connected with it."[10] Participation of God's people in all such pagan rites was strictly forbidden in the Pentateuch. God here promised Israel (Isaiah 17:11) that "grief and desperate sorrow" were the rewards that lay at the end of the road Israel was traveling.