Adam Clarke on Psalms 48:4

For, lo, the kings were assembled - Many of the neighboring potentates, at different times, envied the prosperity of the Jewish nation, and coveted the riches of the temple; but they had no power against it till the cup of Jewish transgression was full. In vain did they assemble - confederate, and invade the land. Saw it - reconnoitered the place; marvelled at its excellence and strength, for they were troubled - struck with fear; hasted away for fear of destruction, for fear took hold on them as pains seize on a woman to travail. Those who came to destroy were glad to make their own escape.