1 Corinthians 10:16 (ESV)

16 The cup of blessing that we bless, is it not a participation in the blood of Christ? The bread that we break, is it not a participation in the body of Christ?

Paul’s use of rhetorical questions indicates that the Corinthians are already familiar with all these teachings.

The Lord’s Supper is a meal in which the participant is united with Christ and his sacrifice on the cross. In that sense, it is itself a sacrificial meal.  

The cup of blessing is a Jewish expression that refers to the cup of wine that would be lifted at the end of a meal. While this cup was lifted, one of the men at the table would customarily say a prayer of thanksgiving, such as, Blessed be you, O Lord, who has created the fruit of the earth. The rest would answer with an Amen or another brief prayer.