Shiloah
Shiloah is the gentle watercourse Isaiah names as a figure for the quiet rule of Yahweh in Jerusalem, set in pointed contrast to the swelling river of Assyria that the prophet sees coming.
The Waters That Go Softly
Isaiah indicts the people for spurning a steady, modest source of water in favor of two foreign powers: "Since this people have refused the waters of Shiloah that go softly, and rejoice in Rezin and Remaliah's son" (Isa 8:6). Shiloah's softness is the point. The waters move quietly, and the prophet treats that quietness as the sign of the kind of help Judah has rejected — not a torrent, not a spectacle, but a sustaining flow that is despised because it is small. Rezin (king of Damascus) and Remaliah's son (Pekah of Israel) stand opposite, and the sentence that follows in Isaiah's oracle brings the great river of Assyria over Judah's neck in their place.