Why does the church share a cup for the wine?

In this passage, what is the significance of partaking of the cup?

Since God required the blood to satisfy His claims (Exodus 12:13; Leviticus 17:11), the cup of blessing expresses fellowship with God. Those partaking of the cup share a fellowship with God on the basis of shed blood. This corporate act expresses a corporate fellowship, "the fellowship" (Acts 2:42) existing when believers obey the Spirit’s teaching, thus forming an assembly (1 Corinthians 1:9).

This is central to Paul’s teaching about idolatry. By partaking of what was given for idols ("the cup of devils"), they expressed a fellowship with demons ("the table of devils"). By symbolically partaking of what was for God ("the cup of the Lord"), they expressed a fellowship with the Lord ("the table of the Lord"). It is morally impossible to have fellowship with devils (demons) and with the Lord, to participate with the heathen temple and with the church of God. Participating in the assembly requires separation from evil.

D. Oliver