Because thou hast forgotten; rather, because thou didst forget. The late repentance of a "remnant" which "looked to their Maker" (Isaiah 17:7) could not cancel the long catalogue of former sins (2 Kings 17:8-17), foremost among which was their rejection of God, or, at any rate, their complete forgetfulness of his claims upon them.
The Rock of thy strength. God is first called "a Rock" in Deuteronomy 32:4, Deuteronomy 32:15, Deuteronomy 32:18, Deuteronomy 32:30, Deuteronomy 32:31. The image is caught up by the psalmists (2 Samuel 22:2, 2 Samuel 22:32, 2 Samuel 22:47; 2 Samuel 23:3; Psalms 16:1, Psalms 16:2, 31, 46; Psalms 19:14; Psalms 28:1, etc.
), and from them passes to Isaiah (see, besides the present passage, Isaiah 26:4; Isaiah 30:29; and Isaiah 44:8). Among the later prophets only Habakkuk uses it (Habakkuk 1:12). Israel, instead of looking to this "Rock," had looked to their rock-fortresses (verse 9).
Therefore shalt thou plant pleasant plants; rather, dost thou plant, or hast thou planted. Forgetfulness of Jehovah has led to the adoption of a voluptuous religion—one of debased foreign rites. There is possibly, as Mr.
Cheyne thinks, a special reference to the cult of Adonis. Shall set it; rather, settest it, or hast set it. "It" must refer to "field" or "garden" understood. The later Israelite religion has been a sort of pleasant garden, planted with exotic slips from various quarters—Phoenicia, Syria, Moab, etc.
It has been thought permissible to introduce into it any new cult that took the fancy. Hence the multiplication of altars complained of by Hosea (Hosea 8:11; Hosea 10:1; Hosea 12:11).