Albert Barnes Commentary Daniel 5:18

"O thou king, the Most High God gave Nebuchadnezzar thy father the kingdom, and greatness, and glory, and majesty:" — Daniel 5:18 (ASV)

O king, the most high God gave Nebuchadnezzar your father a kingdom... This reference to Nebuchadnezzar is evidently designed to show Belshazzar the wickedness of his own course and the reason he had to fear divine vengeance, because he had not learned to avoid the sins which brought so great calamities upon his predecessor.

As Belshazzar was acquainted with what had occurred to Nebuchadnezzar; as he had doubtless seen the proclamation Nebuchadnezzar made on his recovery from the dreadful malady God brought upon him for his pride; and as he had not humbled himself, but had pursued the same course Nebuchadnezzar did, he had greater reason to fear the judgment of heaven. See Daniel 5:22-23.

Daniel here traces all the glory Nebuchadnezzar had to the most high God, reminding the king that for whatever honor and majesty he himself possessed, he was equally indebted for it to the same source, and that he must expect similar treatment from Him.