What does Daniel 5:7 mean?

Belshazzar has entertained a huge party, where he and others have desecrated sacred objects, become drunk, and committed idolatry (Daniel 5:1–4). Without warning, the king sees disembodied fingers writing on the wall on a spot clearly illuminated by a lamp (Daniel 5:5). This inspires abject terror, possibly even causing the king to collapse in fright (Daniel 5:6). His next act is to cry out for help: he seems to know this is a message but does not know what it means.

Frightened people faced with life's mysteries often look for answers wherever they can be found. Not all such answers are true, however. Not all sources are reliable. Faced with the mystery of the handwriting on the wall, Belshazzar shouted for his so-called wise men: the enchanters, the Chaldeans, and the astrologers. These men were sorcerers, scholars, and magicians. It seems the king does not recognize the words written; perhaps they are in some other script. His wise men will also be stumped (Daniel 5:8).

Belshazzar promises that whoever untangles this mystery will be "next in line" in authority behind Belshazzar himself. The mention of being "third ruler" likely connects to Belshazzar's role as interim king. It's likely his father was Nabonidus, the "first ruler," and that he was away and had left Belshazzar as a regent over Babylon. The highest authority to which he can appoint someone, then, would be third. In addition, the horrified king promises wealth and prestige for anyone who can explain this event.