v1: Hezekiah's first response was to tear his clothes, identifying with his people. Apart from the king of Nineveh (Jonah), no other king in the Bible did this. He then went into the temple to pray. Here is a spiritual response.
v2-3: Hezekiah sent his trusted leaders to Isaiah, that he might find the mind of the Lord.
v4: Hezekiah's desire, that the Lord would respond righteously to the words of the king of Assyria.
He made no reference to the large and apparently undefeatable army on his doorstep; he saw the issue as something spiritual, not military, as in 1 Sam 17.26, 36, 45-47. Hezekiah also refers to the remnant of Israel, see 1.9.
v5-6: The first words from God, "Do not be afraid." Such is God's concern for His own. The king of Assyria had blasphemed the Lord; therefore he was doomed to destruction. The Lord was ignorant of neither the king's words, nor His people's predicament.
v7: The specific prophecy about the king, that he would return to his own land, and be killed there; fulfilled v37-38.
v8-10: A new development, taking the field commander away. He sent another message to Hezekiah, this time in a letter read by his messengers.
v11-13: As in 36.18-20, referring to Assyria's past victories. Jerusalem, he claimed, would be swallowed up, just like these other places. See also 30.27-33, where Isaiah prophesies the defeat of Assyria.
v14-15 Hezekiah returned to prayer; a new development, a new message, demanded more prayer. His prayer is based on the uniqueness of God, answering the accusations of the field commander. Hezekiah's prayer shows his love for God and his knowledge of the word of God.
v16: The God who dwells between the cherubim, in the temple in Jerusalem, close to His people. He is the God of all the kingdoms of the earth, He is the creator of all things; these things set the true God apart from all others.
v17: The issue at hand, the blasphemy of Sennacherib; although he was king of Assyria, which Hezekiah does not even mention here, he was just a man; he was therefore helpless before the omnipotent God.
v18-19: Hezekiah acknowledged Assyria's past victories. Their victories had been over nations who trusted in idols; Hezekiah knew the true God, and knew Him to be different.
v20: 'Save us, Lord,' so that the earth might know Him to be the true God; i.e: first as a testimony to His Name, not just for the good of His people.
v21: Again the Lord God gave Hezekiah an answer, "because you have prayed;" for the Lord honours the prayerful attitude.
v22: The Lord gave strength to Jerusalem, the pure virgin daughter. As far as the enemy is concerned, the Lord finds no fault in His people, see Num 23.21 (margin).
v23: The attack by Sennacherib was seen as a blasphemy against the Holy One of Israel; putting the issue into a wider, spiritual, picture.
v24-25: Assyria's successes were attributed to its own powerful army.
v26-27: See 10.5-19; Assyria was ignorant of the plan of God, for Assyria was ignorant of the true God. Assyria had been victorious over many nations (v11-13, 18), but this was ordained by God.
The attack on Jerusalem, and the destruction of the army may well have been a turning point in the fortunes of Assyria. Babylon soon became the new power in the Middle East, and did defeat Jerusalem.
v28-29: The test; that they raged against God, therefore He acted against them.
v30-32: Promises for Hezekiah and Jerusalem in a difficult time. There was famine in the land, brought about by the invading army; they were dependent upon what grew of itself, and the Lord would ensure that that was sufficient. The Lord would preserve the remnant of His people, taking root into God himself, and bearing fruit of faithful lives.
v33-34: Repeated prophecy, that Assyria would return home defeated.
v35: God acted on behalf of His people.
v36-38: God's mighty power to fulfil His own word.