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
4 Kings (2 Kings) 18:1
kg2 18:1HEZEKIAH'S GOOD REIGN. (Kg2 18:1-3)
Hezekiah . . . began to reign. Twenty and five years old--According to this statement (compare Kg2 16:2), he must have been born when his father Ahaz was no more than eleven years old. Paternity at an age so early is not unprecedented in the warm climates of the south, where the human frame is matured sooner than in our northern regions. But the case admits of solution in a different way. It was customary for the later kings of Israel to assume their son and heir into partnership in the government during their lives; and as Hezekiah began to reign in the third year of Hoshea (Kg2 18:1), and Hoshea in the twelfth year of Ahaz (Kg2 17:1), it is evident that Hezekiah began to reign in the fourteenth year of Ahaz his father, and so reigned two or three years before his father's death. So that, at the beginning of his reign in conjunction with his father, he might be only twenty-two or twenty-three, and Ahaz a few years older than the common calculation makes him. Or the case may be solved thus: As the ancient writers, in the computation of time, take notice of the year they mention, whether finished or newly begun, so Ahaz might be near twenty-one years old at the beginning of his reign, and near seventeen years older at his death; while, on the other hand, Hezekiah, when he began to reign, might be just entering into his twenty-fifth year, and so Ahaz would be near fourteen years old when his son Hezekiah was born--no uncommon age for a young man to become a father in southern latitudes [PATRICK].
4 Kings (2 Kings) 18:4
kg2 18:4HE DESTROYS IDOLATRY. (2Ki. 18:4-37)
He removed the high places and brake the images, &c.--The methods adopted by this good king for extirpating idolatry, and accomplishing a thorough reformation in religion, are fully detailed (Ch2 20:3; Ch2 31:19). But they are indicated very briefly, and in a sort of passing allusion.
brake in pieces the brazen serpent--The preservation of this remarkable relic of antiquity (Num 21:5-10) might, like the pot of manna and Aaron's rod, have remained an interesting and instructive monument of the divine goodness and mercy to the Israelites in the wilderness: and it must have required the exercise of no small courage and resolution to destroy it. But in the progress of degeneracy it had become an object of idolatrous worship and as the interests of true religion rendered its demolition necessary, Hezekiah, by taking this bold step, consulted both the glory of God and the good of his country.
unto those days the children of Israel did burn incense to it--It is not to be supposed that this superstitious reverence had been paid to it ever since the time of Moses, for such idolatry would not have been tolerated either by David or by Solomon in the early part of his reign, by Asa or Jehoshaphat had they been aware of such a folly. But the probability is, that the introduction of this superstition does not date earlier than the time when the family of Ahab, by their alliance with the throne of Judah, exercised a pernicious influence in paving the way for all kinds of idolatry. It is possible, however, as some think, that its origin may have arisen out of a misapprehension of Moses' language (Num 21:8). Serpent-worship, how revolting soever it may appear, was an extensively diffused form of idolatry; and it would obtain an easier reception in Israel because many of the neighboring nations, such as the Egyptians and PhÅnicians, adored idol gods in the form of serpents as the emblems of health and immortality.
4 Kings (2 Kings) 18:5
kg2 18:5He trusted in the Lord God of Israel--without invoking the aid or purchasing the succor of foreign auxiliaries like Asa (Kg1 15:18-19) and Ahaz (Kg2 16:17; Isa. 7:1-25).
so that after him was none like him among all the kings of Judah--Of course David and Solomon are excepted, they having had the sovereignty of the whole country. In the petty kingdom of Judah, Josiah alone had a similar testimony borne to him (Kg2 23:25). But even he was surpassed by Hezekiah, who set about a national reformation at the beginning of his reign, which Josiah did not. The pious character and the excellent course of Hezekiah was prompted, among other secondary influences, by a sense of the calamities his father's wicked career had brought on the country, as well as by the counsels of Isaiah.
4 Kings (2 Kings) 18:7
kg2 18:7he rebelled against the king of Assyria--that is, the yearly tribute his father had stipulated to pay, he, with imprudent haste, withdrew. Pursuing the policy of a truly theocratic sovereign, he was, through the divine blessing which rested on his government, raised to a position of great public and national strength. Shalmaneser had withdrawn from Palestine, being engaged perhaps in a war with Tyre, or probably he was dead. Assuming, consequently, that full independent sovereignty which God had settled on the house of David, he both shook off the Assyrian yoke, and, by an energetic movement against the Philistines, recovered from that people the territory which they had taken from his father Ahaz (Ch2 28:18).
4 Kings (2 Kings) 18:13
kg2 18:13Sennacherib--the son and successor of Shalmaneser.
all the fenced cities of Judah--not absolutely all of them; for, besides the capital, some strong fortresses held out against the invader (Kg2 18:17; Kg2 19:8). The following account of Sennacherib's invasion of Judah and the remarkable destruction of his army, is repeated almost verbatim in 2Ch. 32:1-33 and Isa. 36:1-37:38. The expedition seems to have been directed against Egypt, the conquest of which was long a leading object of ambition with the Assyrian monarchs. But the invasion of Judah necessarily preceded, that country being the key to Egypt, the highway through which the conquerors from Upper Asia had to pass. Judah had also at this time formed a league of mutual defense with Egypt (Kg2 18:24). Moreover, it was now laid completely open by the transplantation of Israel to Assyria. Overrunning Palestine, Sennacherib laid siege to the fortress of Lachish, which lay seven Roman miles from Eleutheropolis, and therefore southwest of Jerusalem on the way to Egypt [ROBINSON]. Among the interesting illustrations of sacred history furnished by the recent Assyrian excavations, is a series of bas-reliefs, representing the siege of a town, which the inscription on the sculpture shows to be Lachish, and the figure of a king, whose name is given, on the same inscription, as Sennacherib. The legend, sculptured over the head of the king, runs thus: "Sennacherib, the mighty king, king of the country of Assyria, sitting on the throne of judgment before the city of Lachish [Lakhisha], I give permission for its slaughter" [Nineveh and Babylon]. This minute confirmation of the truth of the Bible narrative is given not only by the name Lachish, which is contained in the inscription, but from the physiognomy of the captives brought before the king, which is unmistakably Jewish.
4 Kings (2 Kings) 18:14
kg2 18:14Hezekiah . . . sent to Lachish, saying, . . . that which thou puttest on me will I bear--Disappointed in his expectations of aid from Egypt, and feeling himself unable to resist so mighty a conqueror who was menacing Jerusalem itself, Hezekiah made his submission. The payment of 300 talents of silver, and 30 talents of gold--Â£351,000--brought a temporary respite; but, in raising the imposed tribute, he was obliged not only to drain all the treasures of the palace and the temple, but even to strip the doors and pillars of the sacred edifice of the gold that adorned them.
4 Kings (2 Kings) 18:17
kg2 18:17SENNACHERIB BESIEGES JERUSALEM. (2Ki. 18:17-37)
king of Assyria sent Tartan--general (Isa 20:1).
Rab-saris--chief of the eunuchs.
Rab-shakeh--chief cupbearer. These were the great officers employed in delivering Sennacherib's insulting message to Hezekiah. On the walls of the palace of Sennacherib, at Khorsabad, certain figures have been identified with the officers of that sovereign mentioned in Scripture. In particular, the figures, Rab-shakeh, Rab-saris, and Tartan, appear as full-length portraits of the persons holding those offices in the reign of Sennacherib. Probably they represent the very individuals sent on this embassy.
with a great host to Jerusalem--Engaged in a campaign of three years in Egypt, Sennacherib was forced by the king of Ethiopia to retreat, and discharging his rage against Jerusalem, he sent an immense army to summon it to surrender. (See on Ch2 32:30).
the conduit of the upper pool--the conduit which went from the reservoir of the Upper Gihon (Birket et Mamilla) to the lower pool, the Birket es Sultan.
the highway of the fuller's field--the public road which passed by that district, which had been assigned them for carrying on their business without the city, on account of the unpleasant smell [KEIL].
4 Kings (2 Kings) 18:18
kg2 18:18when they had called to the king--Hezekiah did not make a personal appearance, but commissioned his three principal ministers to meet the Assyrian deputies at a conference outside the city walls.
Eliakim--lately promoted to be master of the royal household (Isa 22:20).
Shebna--removed for his pride and presumption (Isa 22:15) from that office, though still royal secretary.
Joah . . . the recorder--that is, the keeper of the chronicles, an important office in Eastern countries.
4 Kings (2 Kings) 18:19
kg2 18:19Rab-shakeh said--The insolent tone he assumed appears surprising. But this boasting [Kg2 18:19-25], both as to matter and manner, his highly colored picture of his master's powers and resources, and the impossibility of Hezekiah making any effective resistance, heightened by all the arguments and figures which an Oriental imagination could suggest, has been paralleled in all, except the blasphemy, by other messages of defiance sent on similar occasions in the history of the East.
4 Kings (2 Kings) 18:27
kg2 18:27that they may eat, &c.--This was designed to show the dreadful extremities to which, in the threatened siege, the people of Jerusalem would be reduced.