Isaiah 36:11
Then said Eliakim and Shebna and Joah unto Rabshakeh, Speak, I pray thee, unto thy servants in the Syrian language; for we understand it: and speak not to us in the Jews’ language, in the ears of the people that are on the wall. Then said Eliakim and Shebna and Joah unto Rabshakeh, Speak, I pray thee, unto thy servants in the Syrian language; for we understand it: and speak not to us in the Jews’ language, in the ears of the people that are on the wall.
Eliakim and Shebna and Joah asked Rabshakeh to speak to them in the Syrian language, that is Aramaic, which they understood, rather than in the Jews' language, that is Hebrew or the language of Judah. They made this request so that the people listening from the city wall of Jerusalem would not understand or hear his words.
The request came during the Assyrian officers' direct appeal to the people of Jerusalem. In that siege the envoy deliberately spoke in Hebrew to frighten, discourage, and unsettle the defenders on the wall.
The verse belongs to the historical account of Assyria's threat against Judah during Hezekiah's reign, when the king of Assyria threatened the land. It is part of the account of Sennacherib's invasion and campaign against the land, including the capture of Judah's cities and the threat to Jerusalem, ending in Hezekiah's triumph. That same account records Hezekiah's humility, God's message through the prophet, and the Lord's deliverance from Assyria by His angel. The biblical history of that campaign is confirmed by records recovered from the ruins of Nineveh.