Paul now expounds on the symbol of bread (this is probably the reason why, in 1 Corinthians 10:16, he chose to mention the wine first and then only the bread). The bread symbolizes not only Christ’s body that was broken on the cross, but also Christ’s body as a metaphor for the local church (see also 1 Corinthians 12:12–27). Thus, the bread unites believers not only to Christ’s sacrifice but also to each other.
Evidently, the New Testament church made use of a whole, uncut bread when they celebrated the Lord’s Supper. Pieces of bread would be broken off and distributed. This symbolized that the church is one body.
This is also how Jesus instituted the Supper (Luke 22:19).
17 Puisqu'il y a un seul pain, nous qui sommes plusieurs, nous formons un seul corps; car nous participons tous à un même pain.