"Go wash in the beautiful stream, Go wash in the beautiful stream, Oh, Naaman, oh, Naaman, Go down and wash, Go wash in the beautiful stream."
An allusion to 2 King 5. Naaman, a soldier of Damascus, comes to Israel seeking a cure for his leprosy. He is eventually referred to the prophet Elisha. Elisha tells him to wash himself in the Jordan. Naaman argues, asking why he can't wash in the rivers of Damascus, but eventually does as he's told and is cured.
Naaman did have something of a point: The Jordan valley is not "beautiful"; it is drab, dusty, and very, very hot. - RBW