Charles Ellicott Commentary Daniel 5:13

"Then was Daniel brought in before the king. The king spake and said unto Daniel, Art thou that Daniel, who art of the children of the captivity of Judah, whom the king my father brought out of Judah?" — Daniel 5:13 (ASV)

And the king spake—The words of the queen-mother, especially her mention of the circumstance that Daniel’s name had been changed to Beltehazzar, at once recall the whole of the circumstances to the king’s mind. That Belshazzar knew him by reputation is plain from the description given of him at the end of the verse: which art of the children of the captivity of Judah.

Art thou that Daniel?—He calls him by his Hebrew name, so as to avoid one which sounded so much like his own. Daniel was now nearly ninety years of age.