WCF 29.5.
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; (Matt. 26:26–28) albeit, in substance and nature, they still remain truly and only bread and wine, as they were before. (1 Cor. 11:26–28, Matt. 26:29)