2 Kings 20:15

And he said, What have they seen in thine house? And Hezekiah answered, All the things that are in mine house have they seen: there is nothing among my treasures that I have not shewed them.

Cross-reference

2 Kings 20:13 records what Hezekiah showed the envoys—the very event Isaiah is now questioning him about.

Isaiah 39:3 gives the parallel account of the same dialogue between Isaiah and Hezekiah about the Babylonian visitors.