6 Then the king's countenance  was changed, and his thoughts troubled him, so that the joints of his loins were loosed, and his knees smote one against another.
6 His face turned pale and he was so frightened that his legs became weak and his knees were knocking.
6 Then the king's color changed, and his thoughts alarmed him; his limbs gave way, and his knees knocked together.
6 he went white as a ghost, scared out of his wits. His legs went limp and his knees knocked.
6 Then the king's countenance changed, and his thoughts troubled him, so that the joints of his hips were loosened and his knees knocked against each other.
6 and his face turned pale with fright. His knees knocked together in fear and his legs gave way beneath him.
Matthew Henry's Commentary on Daniel 5:6
Commentary on Daniel 5:1-9
(Read Daniel 5:1-9)
Belshazzar bade defiance to the judgments of God. Most historians consider that Cyrus then besieged Babylon. Security and sensuality are sad proofs of approaching ruin. That mirth is sinful indeed, which profanes sacred things; and what are many of the songs used at modern feasts better than the praises sung by the heathens to their gods! See how God struck terror upon Belshazzar and his lords. God's written word is enough to put the proudest, boldest sinner in a fright. What we see of God, the part of the hand that writes in the book of the creatures, and in the book of the Scriptures, should fill us with awful thoughts concerning that part which we do not see. If this be the finger of God, what is his arm when made bare? And what is He? The king's guilty conscience told him that he had no reason to expect any good news from heaven. God can, in a moment, make the heart of the stoutest sinner to tremble; and there needs no more than to let loose his own thoughts upon him; they will give him trouble enough. No bodily pain can equal the inward agony which sometimes seizes the sinner in the midst of mirth, carnal pleasures, and worldly pomp. Sometimes terrors cause a man to flee to Christ for pardon and peace; but many cry out for fear of wrath, who are not humbled for their sins, and who seek relief by lying vanities. The ignorance and uncertainty concerning the Holy Scriptures, shown by many who call themselves wise, only tend to drive sinners to despair, as the ignorance of these wise men did.