Daniel 2:4 - Joseph Benson’s Commentary on the Old and New Testaments

Then spake the Chaldeans to the king in Syriac The ancient Chaldee and the Syrian language were the same: see Gen 31:47; 2 Kings 18:26; Ezra 4:7. This language is found in its greatest purity in the books of Daniel and Ezra. The following part of the chapter, from this verse, is written in Chaldee, and so on to the end of the seventh chapter: the reason of which seems to be, that what is said from hence to the end of that chapter, relates chiefly to the Chaldeans, or the inhabitants of Babylonia; whereas what follows, from the beginning of the eighth chapter, refers mostly to the Jewish people, and therefore is written in Hebrew.