We hanged our harps upon the willows - The harps once used to accompany the songs of praise and the service of God in the temple; the harps with which they had sought to beguile their weary hours, and to console their sad spirits in their captivity. The word rendered “willows” - ערבים ‛ărâbiym - used only in the plural, denotes the willow or osier, so called from its white, silvery leaves. Gesenius, Lexicon. Compare Isaiah 15:7. It is probable that the weeping willow - the willow with long pendulous branches - is here referred to. Trees in desert lands spring up along the courses of the streams, and appear, in the wide desolation, as long and waving lines of green wherever the rivers wind along. The course of a stream can thus be marked by the prolonged line of meandering green in the desert as far as the eye can reach. It has been objected to the statement here that the willow is not now found in the neighborhood of ancient Babylon, but that the palm is the only tree which grows there. I saw, however, in 1852, in James’ Park in London, a willow-tree with a label on it, stating that it was taken from the site of ancient Babylon; and there seems no reason to doubt the correctness of the account. The willow may be less abundant there now than it was in former times, as is true of the palm. tree in Palestine, but there is no reason to doubt that it grew there. All that the psalm, however, would necessarily demand in a fair interpretation would be that there should have been even a single clump of these trees planted there, under which a little band of exiles may have seated themselves when they gave utterance to the plaintive language of this psalm.
In the midst thereof - In the midst of Babylon; showing that this referred to the city proper. They could not sing, such was their grief, though they had their harps with them; and they hung them up, therefore, on the branches of the trees around them; or, poetically, they were as dumb as if they had hung up their harps there.