Albert Barnes Commentary Daniel 5:26

"This is the interpretation of the thing: MENE; God hath numbered thy kingdom, and brought it to an end;" — Daniel 5:26 (ASV)

Mene - מנא menê'. This word is a passive participle from מנה menâh—"to number, to review" (Gesenius, Lexicon). The verb is also written מנא menâ' (Buxtorf, Lexicon). It would be literally translated "numbered" and would apply to that of which an estimate was taken by counting.

We now use an expression that conveys a similar idea when we say of someone that his days are numbered; that is, he does not have long to live or is about to die. The idea seems to be taken from the fact that the duration of a person’s life cannot usually be known, and in the general uncertainty, we can form no correct estimate of it. However, when someone is old or dangerously sick, we feel that we can, with some degree of probability, number their days, since they cannot live long now. This is the idea here, as explained by Daniel.

All uncertainty about the duration of the kingdom was now removed. Since the evil had come, an exact estimate of its whole duration—of the number of the years of its continuance—could be made. In the Greek of Theodotion, there is no attempt to translate this word, and it is retained in Greek letters—Μανὴ Manē. This is also the case in the Codex Chisianus and in the Latin Vulgate.

God has numbered your kingdom - The word used here and rendered "numbered"—מנה menâh—is the verb of which the previous word is the participle. Daniel applies it to the "kingdom" or "reign" of the monarch, as being a thing of more importance than the life of the king himself. It is evident, if, according to the common interpretation of (Daniel 5:30), Belshazzar was slain that very night, it might have been applied to the king himself, meaning that his days were numbered and that he was about to die. But this interpretation (see Notes) is not absolutely certain. Perhaps the fact that Daniel did not apply the word this way may be properly regarded as one circumstance showing that such an interpretation is not necessary, though it is probably the correct one.

and finished it - This is not the meaning of the word "Mene," but is Daniel's explanation of the thing intended. The word in its interpretation fairly implied this, or this might be understood from it. The fact that the "kingdom" in its duration was "numbered" properly expressed the idea that it was now to come to an end. It did actually come to an end then by being merged into that of the Medes and Persians.