Chapters 36--39 form an historical parenthesis connecting the first part of the book (chapters 1--35) and the last part of the book (chapters 40--66).
In chapter 36 the arrogant conqueror, Sennacherib, openly challenges the Lord and His people and the Assyrian army was overthrown. This is recorded three times--in these chapters, in 2 Kings 18 and 19, and 2 Chronicles 32. This is one of the most astounding miracles of the Old Testament. In one night the Assyrian army is destroyed by a direct stroke from heaven (chapter 37:36). Isaiah had given the assurance in at least nine chapters of his writings that this would take place. Evidently there were two invasions by the Assyrians. Sennacherib, leader of the Assyrian army, invaded Judah in 713 b.c., and took many cities. If we refer to 2 Kings 18:14-16 we see that Hezekiah bought him off at this time, but Sennacherib came again in 701 b.c., at which time Hezekiah, rather than trusting in himself, trusted in the Lord, and the angel smote the Assyrian army (2 Kings 17). If Hezekiah had turned to the Lord at the time of the first invasion, God would have smitten the enemy then.
Chapter 38 covers the time of King Hezekiah's deliverance from serious illness. God promised to add 15 years to the king's life, and confirmed that promise by the sign (verses 4-8). Hezekiah's song of thanksgiving and praise is recorded in verses 9- 20.
In chapter 39 we again see Hezekiah's foolish pride. Isaiah rebuked him for displaying all his wealth and power before the Chaldean, who was pretending to congratulate Hezekiah on his recovery from illness. In verse 6 Isaiah foretells the captivity of Babylon.
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