Adam Clarke on Psalms 46:4

There is a river, the streams whereof - The Chaldee understands the river, and its streams or divisions, as pointing out various peoples who should be converted to the faith and thus make glad the city of God, Jerusalem by their flowing together to the worship of the true God.

But the river may refer to the vast Medo-Persian army and its divisions: those branches which took Babylon; and, instead of ruining and destroying the poor Jews, preserved them alive, and gave them their liberty; and thus the city of God, and the tabernacle of the Most High, were gladdened.