ציטירנדיקער פּירוש אויף תהילים 137:2

by the western sea, they shall take them The enemies shall take them, namely the boundaries. Alternatively, it may be interpreted as: and their visitation; i.e., their visitation that I will bring upon them will be, that to the valley of the willows they shall carry them off. The enemies shall exile them to the land of Babylon, which is the valley of the willows, as it is said (Ps. 137:2): “On willows in its midst we hung our harps.”