Adam Clarke on Isaiah 16:14

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."