This could not refer to the return from exile in Babylon or Assyria. Both were to the east of Israel whereas the psalm envisions believers being gathered from all over the world. It may apply to the regathering of Israelites from all nations in the last days as many other prophecies do (Ezekiel 37:21). It may apply in a broader sense, to the calling of people from every nation through the saving gospel of Christ.

Source:

KJV Defenders Study Bible, by Dr. Henry Morris, Ph.D.
Publisher: Thomas Nelson
Language: English
DEF 10 ISBN 0-529-10444-x
DEF 10-1 ISBN 0-529-10445-8