“Return our exiles, O Lord, like watercourses in the Negev. Those who sow in tears shall reap with songs of joy. He who goes along weeping, carrying the seedbag, shall come back with songs of joy, carrying his sheaves” (Psalm 126:4-6).
In this beautiful and beloved psalm, the return of the exiles to Israel is compared to the “watercourses in the Negev. “Why the Negev and not simply “the desert”? The Negev streams come from collecting basins incomparably larger than those of the Judean Desert. When rain falls on the Negev mountains, water begins to flow into hundreds of tiny rivulets that drain into dozens of larger watercourses. These carry the water, in ever-growing strength, to larger streams that can reach several hundred meters in width.
This picture––myriad tiny rivulets coming together from distant areas to form powerful streams–is surely what inspired the psalmist to pray for the ingathering of the exiles from the four corners of the earth “like watercourses in the Negev.” (See Nogah Hareuveni, Desert and Shepherd in Our Biblical Heritage, p.89-90.)
Those who “sow in tears and reap with songs of joy” is a parallel image. The sowers put each tiny, precious seed into the ground, not knowing whether or not there would be a harvest. And if the blessing of the harvest does come, each seed will have multiplied itself many dozens of times–like the tiny rivulets in the Negev that, together, form rushing streams.
(from website of Neot Kedumim http://www.n-k.org.il/public/english/what/newsletter/2005/donor.htm)