....With St. Augustine:
By use of meat and drink men would fain that " they shall hunger no more, neither thirst any more," and yet there is but one Meat and one Drink, Which doth work in them that feed thereon that " this corruptible must put on incorruption, and this mortal put on immortality," namely communion with that general assembly 2 and Church of God's holy children, who are "kept in perfect peace," and are "all one," fully and utterly. And therefore it is, as men of God before our time have taken it, that our Lord Jesus Christ hath set before us His Body and His Blood in the likeness of things which, from being many, are reduced into one. In one loaf are many grains of corn, and one cup of wine the juice of many grapes. And now He giveth us to know how that which He spake cometh to pass, and how indeed " this Man can give us His Flesh to eat," and His Blood to drink.
He that eateth My Flesh, and drinketh My Blood, dwelleth in Me, and I in him." To dwell in Christ, therefore, and to have Him dwelling in us, is to "eat of that Bread and drink of that Cup," and he which dwelleth not in Christ, and in whom Christ dwelleth not, without all doubt doth not spiritually eat His Flesh nor drink His Blood, although he do carnally and visibly press the Sacrament with his teeth but, contrariwise, he " eateth and drinketh damnation to himself," because he dareth to draw nigh filthy to that secret and holy thing of Christ, whereunto none draweth nigh worthily, save he which is pure, even he which is of them concerning whom it is said " Blessed are the pure in heart, for they shall see God.
As the living Father hath sent Me, and I live by the Father, so he that eateth Me, even he shall live by Me." This is as though He said: The Father hath sent Me into the world and I have emptied Myself [and taken upon Me the form of a servant, and being found in fashion as a man], I have My life from the Father, as One That is greater than I. He that eateth Me, even he, by thereby taking part in Me, shall live by Me. It is as having humbled Myself that I live by the Father, but he that eateth Me, him will I raise up,and so he shall live by Me. It is said "I live by the Father " that is to say, He is of the Father, not the Father of Him, and yet not so, but that the Father and the Son are co-equal together. Also it is said "So he that eateth Me, even he shall live by Me," whereby He showeth the gracious work towards His people of Him Who is the " one Mediator between God and man," and not that He Which is eaten and he which eateth Him are co-equal together.—26th Tract on the Gospel of St. John