But as the blessings of Jesus Christ do not belong to us at all, unless he be previously ours, it is necessary, first of all, that he be given us in the Supper, in order that the things which we have mentioned may be truly accomplished in us. For this reason I am wont to say, that the substance of the sacraments is the Lord Jesus, and the efficacy of them the graces and blessings which we have by his means. Now the efficacy of the Supper is to confirm to us the reconciliation which we have with God through our Saviour’s death and passion; the washing of our souls which we have in the shedding of his blood; the righteousness which we have in his obedience; in short, the hope of salvation which we have in all that he has done for us. It is necessary, then, that the substance should be conjoined with these, otherwise nothing would be firm or certain. Hence we conclude that two things are presented to us in the Supper, viz., Jesus Christ as the source and substance of all good; and, secondly, the fruit and efficacy of his death and passion. This is implied in the words which were used. For after commanding us to eat his body and drink his blood, he adds that his body was delivered for us, and his blood shed for the remission of our sins. Hereby he intimates, first, that we ought not simply to communicate in his body and blood, without any other consideration, but in order to receive the fruit derived to us from his death and passion; secondly, that we can attain the enjoyment of such fruit only by participating in his body and blood, from which it is derived.

via Short Treatise on the Lord’s Supper by John Calvin.