On hearing this report, King Hezekiah tore his clothes, put on sackcloth, and entered the house of the LORD.
The contents of Rabshakeh's speech being brought to Hezekiah, one would have expected (and it is likely Rabshakeh did expect) that he would call a council of war and it would be debated whether it was best to capitulate or no. Before the siege, he had taken counsel with his princes and his mighty men, Ch2 32:3.
Commenting on 2 Kings 19:1-7
And it came to pass, when King Hezekiah heard it,.... The report of Rabshakeh's speech, recorded in the preceding chapter: that he rent his clothes, and covered himself with sackcloth; rent his clothes because of the blasphemy in the speech; and he put on sackcloth, in token of mourning, for the calamities he feared were coming on him and his people: and he went into...
2Ki 19:1-2 When Hezekiah had heard from his counsellors the report of Rabshakeh’s words, he rent his clothes with horror at his daring mockery of the living God (2Ki 19:4), put on mourning clothes as a sign of the trouble of his soul and went into the temple, and at the same time sent Eliakim and Shebna with the oldest of the priests in mourning...
Commenting on 2 Kings 19:1-2