A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
isa 39:1HEZEKIAH'S ERROR IN THE DISPLAY OF HIS RICHES TO THE BABYLONIAN AMBASSADOR. (Isa 39:1-8)
Merodach-baladan--For a hundred fifty years before the overthrow of Nineveh by Cyaxares the Mede, a succession of rulers, mostly viceroys of Assyria, ruled Babylon, from the time of Nabonassar, 747 B.C. That date is called "the Era of Nabonassar." Pul or Phallukha was then expelled, and a new dynasty set up at Nineveh, under Tiglath-pileser. Semiramis, Pul's wife, then retired to Babylon, with Nabonassar, her son, whose advent to the throne of Babylon, after the overthrow of the old line at Nineveh, marked a new era. Sometimes the viceroys of Babylon made themselves, for a time, independent of Assyria; thus Merodach-baladan at this time did so, encouraged by the Assyrian disaster in the Jewish campaign. He had done so before, and was defeated in the first year of Sennacherib's reign, as is recorded in cuneiform characters in that monarchs palace of Koyunjik. Nabopolassar was the first who established, permanently, his independence; his son, Nebuchadnezzar, raised Babylon to the position which Nineveh once occupied; but from the want of stone near the Lower Euphrates, the buildings of Babylon, formed of sun-dried brick, have not stood the wear of ages as Nineveh has.
Merodach--an idol, the same as the god of war and planet Mars (Jer 50:2). Often kings took their names from their gods, as if peculiarly under their tutelage. So Belshazzar from Bel.
Baladan--means "Bel is his lord." The chronicle of EUSEBIUS contains a fragment of BEROSUS, stating that Acises, an Assyrian viceroy, usurped the supreme command at Babylon. Merodach- (or Berodach-) baladan murdered him and succeeded to the throne. Sennacherib conquered Merodach-baladan and left Esar-haddon, his son, as governor of Babylon. Merodach-baladan would naturally court the alliance of Hezekiah, who, like himself, had thrown off the yoke of the Assyrian king, and who would be equally glad of the Babylonian alliance against Assyria; hence arose the excessive attention which he paid to the usurper.
sick--An additional reason is given (Ch2 32:31). "The princes of Babylon sent to enquire of the wonder that was done in the land"; namely, the recession of the shadow on Ahaz' sundial; to the Chaldean astronomers, such a fact would be especially interesting, the dial having been invented at Babylon.
isa 39:2glad--It was not the mere act, but the spirit of it, which provoked God (Ch2 32:25), "Hezekiah rendered not again according to the benefit done unto him, for his heart was lifted up"; also compare Ch2 32:31. God "tries" His people at different times by different ways, bringing out "all that is in their heart," to show them its varied corruptions. Compare David in a similar case (Ch1 21:1-8).
precious things--rather, "the house of his (aromatic) spices"; from a Hebrew root, to "break to pieces," as is done to aromatics.
silver . . . gold--partly obtained from the Assyrian camp (Isa 33:4); partly from presents (Ch2 32:23, Ch2 32:27-29).
precious ointment--used for anointing kings and priests.
armour--or else vessels in general; the parallel passage (Ch2 32:27), "treasuries . . . for shields," favors English Version. His arsenal.
isa 39:3What . . . whence--implying that any proposition coming from the idolatrous enemies of God, with whom Israel was forbidden to form alliance, should have been received with anything but gladness. Reliance on Babylon, rather than on God, was a similar sin to the previous reliance on Egypt (Isa. 30:1-31:9).
far country--implying that he had done nothing more than was proper in showing attention to strangers "from a far country."
isa 39:4All--a frank confession of his whole fault; the king submits his conduct to the scrutiny of a subject, because that subject was accredited by God. Contrast Asa (Ch2 16:7-10).
isa 39:5Lord of hosts--who has all thy goods at His disposal.
isa 39:6days come--one hundred twenty years afterwards. This is the first intimation that the Jews would be carried to Babylon--the first designation of their place of punishment. The general prophecy of Moses (Lev 26:33; Deu 28:64); the more particular one of Ahijah in Jeroboam's time (Kg1 14:15), "beyond the river"; and of Amo 5:27, "captivity beyond Damascus"; are now concentrated in this specific one as to "Babylon" (Mic 4:10). It was an exact retribution in kind, that as Babylon had been the instrument of Hezekiah and Judah's sin, so also it should be the instrument of their punishment.
isa 39:7sons . . . from thee--The sons which Hezekiah (as JOSEPHUS tells us) wished to have (see on Isa 28:3, on "wept sore") will be among the foremost in suffering.
eunuchs--fulfilled (Dan 1:2-3, Dan 1:7).
isa 39:8peace . . . in my days--The punishment was not, as in David's case (Sa2 24:13-15), sent in his time. True repentance acquiesces in all God's ways and finds cause of thanksgiving in any mitigation.
The former were local and temporary in their reference. These belong to the distant future, and are world-wide in their interest; the deliverance from Babylon under Cyrus, which he here foretells by prophetic suggestion, carries him on to the greater deliverance under Messiah, the Saviour of Jews and Gentiles in the present eclectic Church, and the restorer of Israel and Head of the world-wide kingdom, literal and spiritual, ultimately. As Assyria was the hostile world power in the former part, which refers to Isaiah's own time, so Babylon is so in the latter part, which refers to a period long subsequent. The connecting link, however, is furnished (Isa 39:6) at the close of the former part. The latter part was written in the old age of Isaiah, as appears from the greater mellowness of style and tone which pervades it; it is less fiery and more tender and gentle than the former part.