Adam Clarke Bible Commentary
Within three years - בשלש beshalish כשלש keshalish, according, or in or about three years, is the reading of nine of Kennicott's and De Rossi's MSS., and two ancient editions.
But the present reading may well stand: "Now, the Lord hath spoken, saying, Within three years, as the years of a hireling." It seems as if this prophecy had been delivered before, without any time specified for its fulfillment; but now the time is determined" in three years, as the years of a hireling" - for, as a hireling counts even to a single day, and will not abide with his employer an hour beyond the time agreed on; so, in three years, even to a day, from the delivery of this prophecy, shall destruction come upon Moab. This is the import of the present text; but if we take כשלש keshalish, AS in three years, or in about three years' time, the prophecy is not so definite.
These three years, says Calmet, are mentioned from the death of Ahaz, see Isa 14:28, and end the third year of Hezekiah, three years before the taking of Samaria by Shalmaneser. This conqueror did not ruin Moab so completely as not to leave a man in the land; the final desolation of Moab was reserved for Nebuchadnezzar, five years after the taking of Jerusalem.
Feeble "And without strength" - An ancient MS., with the Septuagint, reads ולא velo, "and not."
Jamieson-Fausset-Brown Bible Commentary
three years . . . hireling--Just as a hireling has his fixed term of engagement, which neither he nor his master will allow to be added to or to be taken from, so the limit within which Moab is to fall is unalterably fixed (Isa 21:16). Fulfilled about the time when the Assyrians led Israel into captivity. The ruins of Elealeh, Heshbon, Medeba, Dibon, &c., still exist to confirm the inspiration of Scripture. The accurate particularity of specification of the places three thousand years ago, confirmed by modern research, is a strong testimony to the truth of prophecy.
Already, Tiglath-pileser had carried away the people of Damascus to Kir, in the fourth year of Ahaz (Kg2 16:9); but now in Hezekiah's reign a further overthrow is foretold (Jer 49:23; Zac 9:1). Also, Shalmaneser carried away Israel from Samaria to Assyria (Kg2 17:6; Kg2 18:10-11) in the sixth year of Hezekiah of Judah (the ninth year of Hoshea of Israel). This prophecy was, doubtless, given previously in the first years of Hezekiah when the foreign nations came into nearer collision with Judah, owing to the threatening aspect of Assyria.
Next: Isaiah Chapter 17
John Gill Bible Commentary
But now the Lord hath spoken,.... Something else. What follows is a distinct prophecy from the former, and has a date annexed to it, when it should be fulfilled: the former prophecy relates to the utter destruction of the Moabites by the Babylonians, in the times of Nebuchadnezzar; of which Jeremiah, Jer 48:1 prophesies, in much the same language as Isaiah; and so Jarchi observes, that the final destruction of Moab was by the hand of Nebuchadnezzar: but this was of a lesser nature, and to be accomplished in a short time, either by Shalmaneser, or by Sennacherib king of Assyria, or Esarhaddon his son:
saying, within three years, as the year of an hireling; that is, precisely and exactly three years, neither more nor fewer, neither sooner nor later; as whatever time is agreed upon by an hireling, as soon as ever it is out, which he often thinks of, and counts exactly, he demands his wages, and his freedom. Some think this prophecy bears date with the former, concerning the Philistines, which was the year King Ahaz died, Isa 14:28 and so had its accomplishment in the fourth year of Hezekiah, when Shalmaneser came up against Samaria (k), and took Moab in his way, Kg2 18:9 others, that it was given out in the fourth year of Hezekiah, when the Assyrian besieged Samaria, and after three years took it, and then returned and fell upon the Moabites; others place it in the eleventh year of Hezekiah, and suppose it to be fulfilled in his fourteenth by Sennacherib, about the same time he came up and took the fenced cities of Judah, and besieged Jerusalem, Kg2 18:13 and with this agree the Jewish writers (l), whose words are these,
"after those things, and the establishment thereof, Sennacherib king of Assyria came into Judah, Ch2 32:1 and at the same time sent Tartan to Ashdod, Isa 20:1 who overran the Ammonites and Moabites, who helped him when he besieged Samaria three years, that it might be fulfilled what is said, Isa 16:14 at the same time the king of Assyria sent Rabshakeh from Lachish to Jerusalem.''
Upon which Kimchi observes, as an interpretation of the phrase, "as the years of an hireling",
"it is as if it was said, because they helped the king of Assyria three years against Samaria, it was as if they had been hired; therefore they fell by his hand, and the glory of Moab was light in the hand of the king of Assyria.''
But others make it to be three years after this time; but very likely it might be later still, about the eighteenth or nineteenth year of Hezekiah, as Gataker thinks, who, in his notes on this place, has collected all these senses, and made his observations on them; and so had its accomplishment in some expedition of Esarhaddon, who greatly weakened and impoverished the country of Moab, though he did not destroy it, and which was an earnest and pledge of the utter destruction of it before prophesied of. Noldius renders it, "after three years"; and so Grotius: it was in the first year of Hezekiah, as Noldius observes, that this was said; and in the fourth year of his reign, Shalmaneser came against Samaria, and in his way was the beginning of this destruction, and but a beginning of it, as he observes, yet a pledge of the consummation by Nebuchadnezzar, which was long after these three years of Isaiah.
And the glory of Moab shall be contemned with all that great multitude; of cities and towns, of the inhabitants of them, and of wealth and riches, things in which Moab gloried, and were reckoned weighty and heavy things; these were accounted light by the king of Assyria, who spoiled them, or at least greatly diminished them:
and the remnant shall be very small and feeble; or, "not mighty" or "strong"; those that were not cut off by the Assyrian army would be but few, and these weak and without strength, being dispossessed of their cities, and of their wealth; though, in process of time, between this, and the fulfilment of the former prophecy, and that of Jeremiah, they recovered themselves, and became very numerous and flourishing.
(k) See Prideaux's Connect. par. 1. B. 1. p. 18. So Vitringa. (l) Seder Olam Rabba, c. 23. p. 64.
Next: Isaiah Chapter 17