John Gill's Exposition of the Whole Bible
Isaiah 18:5
For afore the harvest,.... Or vintage: the above metaphor is carried on; before the designs and schemes of the people above described are ripe for execution, who promised themselves a large harvest of their neighbours:
when the bud is perfect; when the bud of the vine is become a perfect grape, though unripe; when the scheme was fully laid, and with perfect and consummate wisdom as imagined, though not brought into execution:
and the sour grape is ripening in the flower; things go on and promise well, as if the issue would be according to expectation, and there would be a good vintage. The sour grape may denote the temper and disposition of the above people against their enemies, their ill nature, and enmity to them; or the sins and transgressions, for which the judgment denounced came upon them:
he shall both cut off the sprigs with pruning hooks, and take away [and] cut down the branches; as the vinedresser; or rather as one that has no good will to the vine, cuts it with pruning hooks, not to make it better, but worse, and cuts off, not the dead withered and useless parts of it, but the sprigs that have buds and flowers, or unripe grapes, upon them, and even whole branches that have clusters on them, and takes them and casts them away, to be trodden under foot, or cast into the fire; so the Lord, or the king of Assyria, the instrument in the hand of God, should cut off the Ethiopians, or the Egyptians, with the sword, both small and great, when their enterprise should fail, and their promised success: or this is to be understood of the destruction of Sennacherib's army by the angel, when he was full of expectation of taking Jerusalem, and plundering that rich city. Jarchi and Kimchi interpret it of the destruction of the armies of Gog and Magog. The Targum is,
"and he shall kill the princes of the people with the sword, and their mighty ones he shall remove and cause to pass over.''