Charles Ellicott Commentary Psalms 126:4

"Turn again our captivity, O Jehovah, As the streams in the South." — Psalms 126:4 (ASV)

Captivity. — Here there is a change. The joy of the great Return was too great not to endure through many difficulties. But the poet now thinks of the many exiles still dispersed among the nations, and prays for another manifestation of Divine favor and power.

The streams in the south. — Rather, the channels in the south. The allusion is to the sudden filling of the dry torrent beds of the southern district of Palestine in the rainy season. So the poet prays that torrents of the returned may pour into the desolate and deserted country. (Compare to Isaiah 49:18 for the same feeling, but under a different figure.) The Septuagint has “in the south wind,” evidently thinking of the melting of a frozen stream, instead of the filling of a dry riverbed.