Charles H. Spurgeon on Psalms 137:1

By the rivers. The bank of a river, like the seashore, is a favourite place of sojourn of those whom deep grief drives forth from the bustle of men into solitude. The boundary line of the river gives to solitude a safe back; the monotonous splashing of the waves keeps up the dull, melancholy alternation of thoughts and feelings; and at the same time the sight of the cool, fresh water exercises a soothing influence upon the consuming fever within the heart. —Franz Delitzsch.