Shocked by the blood on his hands, asking "Will all great Neptune's ocean wash this blood / Clean from my hand? No: this my hand will rather / The multitudinous seas incarnadine, / Making the green one red". He knows their guilt goes beyond the literal "blood" on their "hand[s]", and that nothing can remove the metaphorical "blood" on their souls. The reference to "Neptune", a non-Christian god, could reflect how he has turned his back on God.