C. F. Keil and Franz Delitzsch on 2 Chronicles 32:20

2Ch 32:20 Prayer of King Hezekiah and of the prophet Isaiah for the help of the Lord. - 2Ch 32:20. The main contents of Hezekiah’s prayer are communicated in 2Ki 19:14-19 and Isa 37:15-19. There it is not expressly said that Isaiah also prayed, but it may be inferred from the statement in 2Ki 19:2. and Isa 37:2. that Hezekiah sent a deputation to the prophet with the request that he would pray for the people. In answer Isaiah promised the ambassadors deliverance, as the word of the Lord. זאת על, on account of this, i.e., on account of the contempt shown for the God of Israel, which was emphatically dwelt upon both in the prayer of Hezekiah (2Ki 19:16) and in the word of Isaiah, v. 22ff.