John Gill's Exposition of the Whole Bible
Isaiah 39:4
Then said he, what have they seen in thine house?.... Coming nearer to the point he had in view, and which was the thing that was displeasing to the Lord; not that he had received the ambassadors, and used them in such a manner as persons in such a quality ought to be used; but that he had shown them what he ought not to have done, and especially from such a principle of pride and vanity as he did:
and Hezekiah answered without any reserve, very openly, not suspecting that the prophet was come with a reproof to him, or to blame him, or would blame him for what he had done:
all that is in my house have they seen; the several royal apartments, and the furniture of them:
there is nothing among my treasures that I have not showed them: which were more secret, laid up in cabinets, under lock and key; his gold, silver, jewels, and precious stones, spices, and ointments. Jerom thinks he showed them the furniture and vessels of the temple, though he does not mention them.