This is the interpretation of the thing: MENE; God hath numbered thy kingdom, and finished it.

Wesley's Notes

5:26 MENE - MENE MENE, it is numbered, it is numbered; the words are doubled for the greater confirmation. It relates to the number of the seventy years for the overthrow of the Babylonish empire.

Jamieson-Fausset-Brown Bible Commentary

26. God hath fixed the number of years of thine empire, and that number is now complete.

Matthew Henry's Concise Commentary

5:18-31 Daniel reads Belshazzar's doom. He had not taken warning by the judgments upon Nebuchadnezzar. And he had insulted God. Sinners are pleased with gods that neither see, nor hear, nor know; but they will be judged by One to whom all things are open. Daniel reads the sentence written on the wall. All this may well be applied to the doom of every sinner. At death, the sinner's days are numbered and finished; after death is the judgment, when he will be weighed in the balance, and found wanting; and after judgment the sinner will be cut asunder, and given as a prey to the devil and his angels. While these things were passing in the palace, it is considered that the army of Cyrus entered the city; and when Belshazzar was slain, a general submission followed. Soon will every impenitent sinner find the writing of God's word brought to pass upon him, whether he is weighed in the balance of the law as a self-righteous Pharisee, or in that of the gospel as a painted hypocrite.