And he sent Eliakim the palace administrator, Shebna the scribe, and the leading priests, all wearing sackcloth, to the prophet Isaiah son of Amoz
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 he sent Eliakim, which [was] over the household, and Shebna the scribe, and the elders of the priests, covered with sackcloth, to Isaiah the prophet the son of Amoz. (a) To hear some new prophecy and to have comfort from him.
To Isaiah the prophet - His fame and influence were at this time great in Israel; and it was well known that the word of the Lord was with him. Here both the Church and the state unite in fervent application to, and strong dependence upon, God; and behold how they succeed!