John Gill Commentary Psalms 48:6

"Trembling took hold of them there, Pain, as of a woman in travail." — Psalms 48:6 (ASV)

Fear took hold upon them there
That is, either when they came up to the city, and passed by it, and saw what they did; or, as Kimchi observes, in the place where they thought to have made a great slaughter; that is, in Armageddon, (Revelation 16:16) ; so upon the slaughter of the seven thousand names of men, or men of name and renown, such as the kings here assembled, the remnant will be frightened, (Revelation 11:13) ;

[and] pain, as of a woman in travail ;
this figure is made use of elsewhere, when the destruction of Babylon and the coming of Christ are spoken of; see (Isaiah 13:8) (1 Thessalonians 5:2 1 Thessalonians 5:3) .