Isaiah 37:9

And he heard say concerning Tirhakah king of Ethiopia, He is come forth to make war with thee. And when he heard it, he sent messengers to Hezekiah, saying,

Cross-reference

2 Kings 19:8 is the parallel account of the same event — Rabshakeh returns to find the Assyrian king fighting at Libnah.

2 Kings 19:9 repeats the same report about Tirhakah and the sending of messengers — a direct parallel to this verse.