From Calvin’s Short Treatise on the Supper of Our Lord, section 12:
We begin now to enter on the question so much debated, both anciently and at the present time—how we are to understand the words in which the bread is called the body of Christ, and the wine his blood. This may be disposed of without much difficulty, if we carefully observe the principle which I lately laid down, viz., that all the benefit which we should seek in the Supper is annihilated if Jesus Christ be not there given to us as the substance and foundation of all. That being fixed, we will confess, without doubt, that to deny that a true communication of Jesus Christ is presented to us in the Supper, is to render this holy sacrament frivolous and useless—an execrable blasphemy unfit to be listened to.
From Knox’s The Scottish Confession of Faith, section 21:
And these sacraments (as well of the Old as of the New Testament) were instituted of God, not only to make a visible difference betwixt his people, and those that were without his league; but also to exercise the faith of his children and, by participation of the same sacraments, to seal in their hearts the assurance of his promise, and of that most blessed conjunction, union, and society, which the elect have with their head, Christ Jesus.
And thus we utterly damn the vanity of those that affirm sacraments to be nothing else but naked and bare signs. No, we assuredly believe that by baptism we are engrafted in Christ Jesus, to be made partakers of his justice, by the which our sins are covered and remitted; and also, that in the supper, rightly used, Christ Jesus is so joined with us, that he becomes the very nourishment and food of our souls. (1 Cor. 10:16; Rom. 6:3-5; Gal. 3:27.)
From the Westminster Confession of Faith, sections 27, 28, 29:
I. Sacraments are holy signs and seals of the covenant of grace, immediately instituted by God, to represent Christ and His benefits; and to confirm our interest in Him: as also, to put a visible difference between those that belong unto the Church and the rest of the world; and solemnly to engage them to the service of God in Christ, according to His Word.
II. There is, in every sacrament, a spiritual relation, or sacramental union, between the sign and the thing signified: whence it comes to pass, that the names and effects of the one are attributed to the other.
I. Baptism is a sacrament of the New Testament, ordained by Jesus Christ, not only for the solemn admission of the party baptized into the visible Church; but also to be unto him a sign and seal of the covenant of grace, of his ingrafting into Christ, of regeneration, of remission of sins, and of his giving up unto God, through Jesus Christ, to walk in the newness of life. Which sacrament is, by Christ’s own appointment, to be continued in His Church until the end of the world.
I. Our Lord Jesus, in the night wherein He was betrayed, instituted the sacrament of His body and blood, called the Lord’s Supper, to be observed in His Church, unto the end of the world, for the perpetual remembrance of the sacrifice of Himself in His death; the sealing all benefits thereof unto true believers, their spiritual nourishment and growth in Him, their further engagement in and to all duties which they owe unto Him; and, to be a bond and pledge of their communion with Him, and with each other, as members of His mystical body.
VII. Worthy receivers, outwardly partaking of the visible elements, in this sacrament, do then also, inwardly by faith, really and indeed, yet not carnally and corporally but spiritually, receive and feed upon, Christ crucified, and all benefits of His death: the body and blood of Christ being then, not corporally or carnally, in, with, or under the bread and wine; yet, as really, but spiritually, present to the faith of believers in that ordinance, as the elements themselves are to their outward senses.
I don’t know… we are uncomfortable with what is a vital part of sacraments to Calvin, Knox and the Westminster divines, we are very “spiritual”, they are both spiritual but also more “earthy”? Why are we so Zwinglian?