Isaiah 1:18

Come now, and let us reason together. — The Authorised Version suggests the thought of a discussion between equals. The Hebrew implies rather the tone of one who gives an authoritative ultimatum, as from a judge to the accused, who had no defence, or only a sham defence, to offer (Micah 6:2). “Let us sum up the pleadings — that ultimatum is one of grace and mercy — ‘Repent, and be forgiven.’”

Though your sins be as scarlet. — The two colours probably corresponded to those now designated by the English words. Both words point to the dyes of Tyre, and the words probably received a fresh emphasis from the fact that robes of these colours were worn by the princes to whom Isaiah preached (2 Samuel 1:24). To the prophet’s eye that dark crimson was as the stain of blood. What Jehovah promises is that the guilt of the past, deep-dyed in grain as it might be, should be discharged, and leave the character with a restored purity. Men might dye their souls of this or that hue, but to bleach them was the work of God. He alone could transfigure them that they should be “white as snow” (Mark 9:3). Comp. the reproduction of the thought, with the added paradox that it was the crimson “blood of the lamb” that was to bleach and cleanse, in Revelation 3:4; Revelation 7:14.