Why does the priest mix a small amount of water with the wine to be consecrated?

Answer: The mingling signifies the union of the divine and human natures of Christ, as is beautifully expressed in the prayer then said by the priest, “By the mystery of this water and wine may we come to share in the divinity of Christ, who humbled himself to share in our humanity.” This mingling also signifies our union with Him in Holy Communion.