Although Hezekiah brought revival to Judah, his reign was not without problems. Troubles come to the just and to the unjust; the difference is that God brings deliverance for the just. This builds His children's faith and brings Him the glory He deserves. The Assyrian invasion of Judah and their threat of taking Jerusalem were certainly trials for Hezekiah, testing his faith. He immediately strengthened the fortifications of the city and made additional weapons when he heard that the Assyrian army was coming to lay seige to Jerusalem. The prophet Isaiah rebuked him for this, since it showed a dependence upon their own strength rather than on God (Isaiah 22:9-11). Another measure Hezekiah took because of the Assyrian threat was to plug the springs outside the city wall. In an ingenious way, he had an underground tunnel cut out of the rock to bring water from the spring of Gihon to the Pool of Siloam within the city in case there was a long seige (32:3-4, 30).
Isaiah's words must have influenced Hezekiah for he later encouraged the military leaders. His words attested to his faith that God was able to deliver them, no matter how outnumbered they might be. Sennacherib was fighting with an "arm of flesh" (in the natural realm), but Hezekiah was fighting with the arm of the Spirit of God (in the spiritual realm, 32:7-8; cf. Ephesians 6:10-12; 2 Corinthians 10:3-5). At that point, Judah's military strength had been weakened because of the many losses under the reign of Ahaz.
The parallel account in 2 Kings 18:13-19:37 gives more details of the Assyrian invasion and Hezekiah's reaction. Chronicles gives a summary of the events and a shorter version of Sennacherib's threats, spoken by his representative, in which he blasphemed the God of Israel, saying no power could stop him. By shouting these abuses in the Hebrew vernacular, he attempted to bring about the surrender of the city. Hezekiah fervently prayed, and with Isaiah's admonitions he was encouraged in his faith. The Lord heard their prayers; the death angel visited the Assyrian camp and a great number died. The living and all-powerful God judged them for their sin of blasphemy; He will not be mocked (for a supplementary analysis see commentary on 2 Kings 18 & 19).
As with King Solomon, Hezekiah's fame spread and during his reign the nation became very prosperous. In the account of Hezekiah's reign, the chronicler is careful to note that the reason for Hezekiah's success was that he honoured God, sought Him with his whole heart, and obeyed His Law (31:21; 32:22, 29). However, Hezekiah was not without sin: on two occasions his pride had been a problem, but because he humbled himself before the Lord, the wrath of God upon Judah was postponed (for further details see commentary on 2 Kings 20).
Sadly, Hezekiah's son Manasseh was one of the most wicked kings of Judah. He brought back idolatry and seduced the nation to do more evil than the Canaanites who had occupied the land before them. He filled the land with idolatry and desecrated the Temple with idols. Like his grandfather Ahaz, Manasseh practiced human sacrifice, and worshipped Baal. He also delved into all manners of occultism, including consulting witches, but ignored the warnings of God's prophets (33:10). The Lord gave him the longest reign of any king of Judah, thus giving him ample time to repent and serve Him.
Eventually, the Lord brought Manasseh to his knees, but it took his own captivity and imprisonment in Babylon. Upon his sincere repentance, the Lord lifted him up and restored him as king in Judah (33:11-13). The grace and forgiveness of the Lord is truly amazing! Manasseh's religious reforms attested to the sincerity of his repentance and conversion. When one is truly repentant before the Lord, his actions will reflect the change in his heart.
Manasseh's son Amon, however, patterned his life after his father's evil days. The result? He had a very short reign of only two years and was assassinated. Sadly, he never humbled himself before the Lord nor repented of his sin.