Turn again our captivity, O LORD, as the streams in the south. Turn again our captivity - This is either a recital of the prayer they had used before their deliverance; or it is a prayer for those who still remained in the provinces beyond the Euphrates. The Jewish captives did not all return at once; they came back at different times, and under different leaders, Ezra, Nehemiah, Zerubbabel, etc.
As the streams in the south - Probably the Nile is meant. It is now pretty well known that the Nile has its origin in the kingdom of Damot; and runs from south to north through different countries, till, passing through Egypt, it empties itself into the Mediterranean Sea. It it possible, however, that they might have had in view some rapid rivers that either rose in the south, or had a southern direction; and they desired that their return might be as rapid and as abundant as the waters of those rivers. But we know that the Nile proceeds from the south, divides itself into several streams as it passes through Egypt, and falls by seven mouths into the Mediterranean.