It may be that the LORD your God heard all the words of the Rabshakeh, whom his master the king of Assyria has sent to mock the living God, and will rebuke the words that the LORD your God has heard; therefore lift up your prayer for the remnant that is left.”
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
the living God--"The living God" is a most significant expression taken in connection with the senseless deities that Rab-shakeh boasted were unable to resist his master's victorious arms.
It may be the LORD thy God will hear all the words of Rabshakeh, whom the king of Assyria his master hath sent to reproach the living God; and will reprove the words which the LORD thy God hath heard: wherefore lift up [thy] prayer for the remnant that are left. (c) Meaning, for Jerusalem which only remained of all the cities of Judah.