By thy servants hast thou reproached the Lord, and hast said, By the multitude of my chariots am I come up to the height of the mountains, to the sides of Lebanon; and I will cut down the tall cedars thereof, and the choice fir trees thereof: and I will enter into the height of his border, and the forest of his Carmel.
Hast thou ... said - virtually. Hast thou said within thyself.
Height of the mountains, to the sides of Lebanon - imagery from the Assyrian felling of trees in Lebanon (Isaiah 14:8; Isaiah 33:9); figurative for, 'I have carried my victorious army through the regions most difficult of access, to the most remote lands.'
Fir trees - not cypresses, as some translate. Pine foliage and cedars are still found on the northwest side of Lebanon (Stanley). The Chaldaic paraphrases, 'I will ascend to the stronghold of their cities, and moreover I will take the house of their sanctuary ("Lebanon"), and I will kill the fairest among their brave men' (answering to the tall cedars).
The height of his border - in 2 Kings 19:23, "the lodgings of his borders." Perhaps on the ascent to the top there was a place of repose or caravansera, which bounded the usual attempts of persons to ascend, (Barnes). Here, simply, 'its extreme height;' 'the height of his summit' (Vulgate).
The forest of his Carmel - or else, 'its thickest forest.' Carmel expresses thick luxuriance (note, Isaiah 10:18; Isaiah 29:17). The Chaldaic paraphrases, 'the multitude of their army.'