My heart panted, fearfulness terrified me: the night {g} of my pleasure hath he turned into fear to me.

(g) He prophecies the death of Belshazzar as in Dan 5:30 who in the midst of his pleasures was destroyed.

Wesley's Notes

21:4 The night - In which I used to have sweet repose. He seems to have had this vision in a night. But withal this signified that horror and destruction, which should befal the Babylonians in a night of feasting and jollity. He - God, who shewed him that vision.

King James Translators' Notes

heart...: or, mind wandered

turned: Heb. put

Jamieson-Fausset-Brown Bible Commentary

4. panted-"is bewildered" [Barnes].

night of my pleasure-The prophet supposes himself one of the banqueters at Belshazzar's feast, on the night that Babylon was about to be taken by surprise; hence his expression, "my pleasure" (Isa 14:11; Jer 51:39; Da 5:1-31).

Matthew Henry's Concise Commentary

21:1-10 Babylon was a flat country, abundantly watered. The destruction of Babylon, so often prophesied of by Isaiah, was typical of the destruction of the great foe of the New Testament church, foretold in the Revelation. To the poor oppressed captives it would be welcome news; to the proud oppressors it would be grievous. Let this check vain mirth and sensual pleasures, that we know not in what heaviness the mirth may end. Here is the alarm given to Babylon, when forced by Cyrus. An ass and a camel seem to be the symbols of the Medes and Persians. Babylon's idols shall be so far from protecting her, that they shall be broken down. True believers are the corn of God's floor; hypocrites are but as chaff and straw, with which the wheat is now mixed, but from which it shall be separated. The corn of God's floor must expect to be threshed by afflictions and persecutions. God's Israel of old was afflicted. Even then God owns it is his still. In all events concerning the church, past, present, and to come, we must look to God, who has power to do any thing for his church, and grace to do every thing that is for her good.