WCF 29.8.
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 thereunto, are guilty of the body 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, (1 Cor. 11:27–29, 2 Cor. 6:14, 16) or be admitted thereunto. (1 Cor. 5:6–7, 13, 2 Thess. 3:6, 14–15, Matt. 7:6)