1 Corinthians 10:16 - Matthew Poole's English Annotations on the Holy Bible

It is on all hands agreed, that the apostle is here speaking of believers communicating in the sacrament of the Lord's supper. By the cup of blessing, he meaneth the cup there, which he so calleth, because we in the taking of it bless the Lord, who gave his Son to die for us, and Christ, for that great love which he showed in dying for us: we are said to bless it, because we, by solemn prayer in the consecration of it, set it apart for that sacred use, and beg of God to bless it to us. This cup (saith the apostle) is the communion of the blood of Christ. The cup is put for the wine in the cup (which is very ordinary). The cup, or wine, of blessing, signifieth that cup of wine to which the blessing is added, or with which in that holy institution we thankfully remember the death of Christ, and bless his name for that great mercy; and the wine or cup of blessing, also, here signifieth our religions action in drinking of that cup of wine so blessed. This, saith he, is the communion of the blood of Christ; that is, it is an action whereby and wherein Christ communicates himself and his grace to us, and we communicate our souls to him; so that Christ and believers in that action have a mutual communion one with another. And as it is with the one element in that holy sacrament, so it is also with the other. The bread which the minister breaketh (according to the institution and example of Christ) for the church to make use of in the celebration of the Lord's supper, that is, their action in eating of that bread so broken and divided amongst them, is the communion of the body of Christ; an action wherein Christians have a fellowship and communion with Christ.