From the Westminster Confession of Faith:

Of The Sacraments

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 to the Church and the rest of the world; and solemnly to engage them to the service of God in Christ, according to His Word. 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. The grace which is exhibited in or by the sacraments rightly used, is not conferred by any power in them; neither does the efficacy of a sacrament depend upon the piety or intention of him that does administer it: but upon the work of the Spirit, and the word of institution, which contains, together with a precept authorizing the use of it, a promise of benefit to worthy receivers. There are only two sacraments ordained by Christ our Lord in the Gospel; that is to say, Baptism, and the Supper of the Lord: neither of which may be dispensed by any, but by a minister of the Word lawfully ordained. The sacraments of the Old Testament in regard to the spiritual things thereby signified and exhibited, were, for substance, the same with those of the new.

Of Baptism

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 to 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 to 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.
II. The outward element to be used in this sacrament is water, wherewith the party is to be baptized, in the name of the Father, and of the Son, and of the Holy Spirit, by a minister of the Gospel, lawfully called to it.
III. Dipping of the person into the water is not necessary; but Baptism is rightly administered by pouring, or sprinkling water upon the person.
IV. Not only those that do actually profess faith in and obedience to Christ, but also the infants of one, or both, believing parents, are to be baptized.
V. Although it is a great sin to condemn or neglect this ordinance, yet grace and salvation are not so inseparably annexed to it, as that no person can be regenerated, or saved, without it: or, that all that are baptized are undoubtedly regenerated.
VI. The efficacy of Baptism is not tied to that moment of time wherein it is administered; yet, notwithstanding, by the right use of this ordinance, the grace promised is not only offered, but really exhibited, and conferred, by the Holy Spirit, to such (whether of age or infants) as that grace belongs to, according to the counsel of God’s own will, in His appointed time.
VII. The sacrament of Baptism is but once to be administered to any person.

Of The Lord’s Supper, Communion

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, to the end of the world, for the perpetual remembrance of the sacrifice of Himself in His death; the sealing all benefits of it to true believers, their spiritual nourishment and growth in Him, their further engagement in and to all duties which they owe to Him; and, to be a bond and pledge of their communion with Him, and with each other, as members of His mystical body.
II. In this sacrament, Christ is not offered up to His Father; nor any real sacrifice made at all, for remission of sins of the quick or dead; but only a commemoration of that one offering up of Himself, by Himself, upon the cross, once for all: and a spiritual oblation of all possible praise to God, for the same: so that the popish sacrifice of the mass (as they call it) is most abominably injurious to Christ’s one, only sacrifice, the alone propitiation for all the sins of His elect.
III. The Lord Jesus has, in this ordinance, appointed His ministers to declare His word of institution to the people, to pray, and bless the elements of bread and wine, and thereby to set them apart from a common to an holy use; and to take and break the bread, to take the cup, and (they communicating also themselves) to give both to the communicants; but to none who are not then present in the congregation.
IV. Private masses, or receiving this sacrament by a priest, or any other alone; as likewise, the denial of the cup to the people, worshiping the elements, the lifting them up, or carrying them about, for adoration, and the reserving them for any pretended religious use; are all contrary to the nature of this sacrament, and to the institution of Christ.
V. The outward elements in this sacrament, duly set apart to the uses ordained by Christ, have such relation to Him crucified, as that, truly, yet sacramentally only, they are sometimes called by the name of the things they represent, to wit, the body and blood of Christ; albeit, in substance and nature, they still remain truly and only bread and wine, as they were before.
VI. That doctrine which maintains a change of the substance of bread and wine, into the substance of Christ’s body and blood (commonly called transubstantiation) by consecration of a priest, or by any other way, is repugnant, not to Scripture alone, but even to common sense, and reason; overthrows the nature of the sacrament, and has been, and is, the cause of manifold superstitions; yes, of gross idolatries.
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.
VIII. Although ignorant and wicked men receive the outward elements in this sacrament; yet, they receive not the thing signified thereby; but, by their unworthy coming to it, are guilty of the body and blood of the Lord, to their own damnation. Wherefore, all ignorant and ungodly persons, as they are unfit to enjoy communion with Him, so are they unworthy of the Lord’s table; and cannot, without great sin against Christ, while they remain such, partake of these holy mysteries, or be admitted to it.