1 Corinthians 10:16

The cup of blessing--answering to the Jewish "cup of blessing," over which thanks were offered in the Passover. It was in doing so that Christ instituted this part of the Lord's Supper (Mat 26:27; Luk 22:17, Luk 22:20). we bless--"we," not merely ministers, but also the congregation. The minister "blesses" (that is, consecrates with blessing) the cup, not by any priestly transmitted authority of his own, but as representative of the congregation, who virtually through him bless the cup. The consecration is the corporate act of the whole Church. The act of joint blessing by him and them (not "the cup" itself, which, as also "the bread," in the Greek is in the accusative), and the consequent drinking of it together, constitute the communion, that is, the joint participation "of the blood of Christ." Compare Co1 10:18, "They who eat . . . are partakers" (joint communicants). "Is" in both cases in this verse is literal, not represents. He who with faith partakes of the cup and the bread, partakes really but spiritually of the blood and body of Christ (Eph 5:30, Eph 5:32), and of the benefits of His sacrifice on the cross (compare Co1 10:18). In contrast to this is to have "fellowship with devils" (Co1 10:20). ALFORD explains, "The cup . . . is the [joint] participation (that is, that whereby the act of participation takes place) of the blood," &c.

— Jamieson-Fausset-Brown Commentary (public domain)