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
2 Chronicles 32:1
ch2 32:1SENNACHERIB INVADES JUDAH. (2Ch. 32:1-20)
After these things, and the establishment thereof--that is, the restoration of the temple-worship. The precise date is given, Kg2 18:13. Determined to recover the independence of his country, Hezekiah had decided to refuse to pay the tribute which his father had bound himself to pay to Assyria.
Sennacherib . . . entered into Judah, and encamped against the fenced cities--The whole land was ravaged; the strong fortresses of Ashdod (Isa 20:1) and Lachish had fallen; the siege of Libnah had commenced, when the king of Judah, doubting his ability to resist, sent to acknowledge his fault, and offer terms of submission by paying the tribute. The commencement of this Assyrian war was disastrous to Hezekiah (Kg2 18:13). But the misfortunes of the early period of the war are here passed over, as the historian hastens to relate the remarkable deliverance which God wrought for His kingdom of Judah.
2 Chronicles 32:2
ch2 32:2when Hezekiah saw that Sennacherib . . . was purposed to fight against Jerusalem--An account of the means taken to fortify Jerusalem against the threatened siege is given only in this passage. The polluting or filling up of wells, and the altering of the course of rivers, is an old practice that still obtains in the wars of the East. Hezekiah's plan was to cover the fountain heads, so that they might not be discovered by the enemy, and to carry the water by subterranean channels or pipes into the city--a plan which, while it would secure a constant supply to the inhabitants, would distress the besiegers, as the country all around Jerusalem was very destitute of water.
2 Chronicles 32:4
ch2 32:4So there was gathered much people . . . who stopped all the fountains, and the brook that ran through the midst of the land--"Where these various fountains were, we have now no positive means of ascertaining; though En-rogel, and the spring now called the Virgin's Fount, may well be numbered among them. JOSEPHUS mentions the existence of various fountains without the city, but does not mention any of them in this connection but Siloam. 'The brook,' however, is located with sufficient precision to enable us to trace it very definitely. We are told that it 'ran through the midst of the land.' Now a stream running through either the Kedron or Hinnom Valley, could, in no proper sense, be said to run through the midst of the land, but one flowing through the true Gihon valley, and separating Akra and Zion from Bezetha, Moriah, and Ophel, as a stream once, doubtless, did, could, with peculiar propriety, be said to run through the midst of the land on which the [Holy] City was built. And that this is the correct meaning of the phrase is not only apparent from the force of circumstances, but is positively so declared in the Septuagint, where, moreover, it is called a 'river,' which, at least, implies a much larger stream than the Kedron, and comports well with the marginal reading, where it is said to overflow through the midst of the land. Previous to the interference of man, there was, no doubt, a very copious stream that gushed forth in the upper portion of that shallow, basin-like concavity north of Damascus Gate, which is unquestionably the upper extremity of the Gihon valley, and pursuing its meandering course through this valley, entered the TyropÅon at its great southern curve, down which it flowed into the valley of the Kedron" [BARCLAY, City of the Great King].
2 Chronicles 32:5
ch2 32:5he strengthened himself--He made a careful inspection of the city defenses for the purpose of repairing breaches in the wall here, renewing the masonry there, raising projecting machines to the towers, and especially fortifying the lower portion of Zion, that is, Millo, "(in) the original city of David." "In" is a supplement of our translators, and the text reads better without it, for it was not the whole city that was repaired, but only the lower portion of Zion, or the original "city of David."
2 Chronicles 32:6
ch2 32:6he . . . gathered them together . . . in the street--that is, the large open space at the gate of Eastern cities. Having equipped his soldiers with a full suit of military accoutrements, he addressed them in an animated strain, dwelling on the motives they had to inspire courage and confidence of success, especially on their consciousness of the favor and helping power of God.
2 Chronicles 32:9
ch2 32:9(See on 2Ki. 18:17-35; also 2Ki. 19:8-34).
2 Chronicles 32:18
ch2 32:18they cried with a loud voice . . . unto the people of Jerusalem . . . on the wall--It appears that the wall on the west side of the city reached as far to the side of the uppermost pool of Gihon at that time as it does now, if not farther; and the wall was so close to that pool that those sent to negotiate with the Assyrian general answered him in their own tongue (see on Kg2 18:27).
2 Chronicles 32:21
ch2 32:21AN ANGEL DESTROYS THE ASSYRIANS. (Ch2 32:21-23)
an angel . . . cut off all the mighty men--(See on Kg2 19:35-37).
2 Chronicles 32:24
ch2 32:24HEZEKIAH'S SICKNESS AND RECOVERY. (Ch2 32:24-26)
In those days Hezekiah was sick to the death--(See on Kg2 20:1-11).
2 Chronicles 32:27
ch2 32:27HIS RICHES AND WORKS. (Ch2 32:27-33)
he had exceeding much riches and honour--(compare Kg2 20:13; Isa 39:2). A great portion of his personal wealth, like that of David and Uzziah, consisted in immense possessions of agricultural and pastoral produce. Besides, he had accumulated large treasures in gold, silver, and precious things, which he had taken as spoils from the Philistines, and which he had received as presents from neighboring states, among which he was held in great honor as a king under the special protection of Heaven. Much of his great wealth he expended in improving his capital, erecting forts, and promoting the internal benefit of his kingdom.
2 Chronicles 32:30
ch2 32:30stopped the . . . watercourse of Gihon, and brought it . . . to the west side of the city, &c.--(Compare Kg2 20:20). Particular notice is here taken of the aqueduct, as among the greatest of Hezekiah's works. "In exploring the subterranean channel conveying the water from Virgin's Fount to Siloam, I discovered a similar channel entering from the north, a few yards from its commencement; and on tracing it up near the Mugrabin gate, where it became so choked with rubbish that it could be traversed no farther, I there found it turn to the west in the direction of the south end of the cleft, or saddle, of Zion, and if this channel was not constructed for the purpose of conveying the waters of Hezekiah's aqueduct, I am unable to suggest any purpose to which it could have been applied. Perhaps the reason why it was not brought down on the Zion side, was that Zion was already well-watered in its lower portion by the Great Pool, 'the lower pool of Gihon.' And accordingly WILLIAMS [Holy City] renders this passage, 'He stopped the upper outflow of the waters of Gihon, and led them down westward to the city'" [BARCLAY, City of the Great King]. The construction of this aqueduct required not only masonic but engineering skill; for the passage was bored through a continuous mass of rock. Hezekiah's pool or reservoir made to receive the water within the northwest part of the city still remains. It is an oblong quadrangular tank, two hundred forty feet in length, from one hundred forty-four to one hundred fifty in breadth, but, from recent excavations, appears to have extended somewhat farther towards the north.
2 Chronicles 32:31
ch2 32:31in the business of the ambassadors who sent . . . to inquire of the wonder that was done in the land, &c.--They brought a present (Ch2 32:23; see on Kg2 20:12-13), and a letter of congratulation on his recovery, in which particular enquiries were made about the miracle of the sun's retrocession--a natural phenomenon that could not fail to excite great interest and curiosity at Babylon, where astronomy was so much studied. At the same time, there is reason to believe that they proposed a defensive league against the Assyrians.
God left him, to try him, &c.--Hezekiah's offense was not so much in the display of his military stores and treasures, as in not giving to God the glory both of the miracle and of his recovery, and thus leading those heathen ambassadors to know Him.