Hebrews 9:19

He took the blood of calves — Or heifers. And of goats, with water, and scarlet wool, and hyssop — All these circumstances are not particularly mentioned in that chapter of Exodus, but are supposed to be already known from other passages of Moses. And the book itself — Which contained all he had said. And sprinkled all the people — Who were near him. The blood was mixed with water to prevent its growing too stiff for sprinkling; perhaps also to typify that blood and water, John 19:34. Exodus 24:7