"certain blasphemous suggestions rose into his mind, respecting the communion-supper"
Communion wafer
Creative Commons Attribution Share AlikeCommunion wafer - Credit: York Minster

The communion supper is another name for the Eucharist, a Christian sacrament that enacts Jesus' instructions to the apostles at the Last Supper:

Jesus took bread, and blessed it, and brake it, and gave it to the disciples, and said, Take, eat; this is my body. And he took the cup, and gave thanks, and gave it to them, saying, Drink ye all of it; For this is my blood of the new testament, which is shed for many for the remission of sins. (Matthew 26:26-8).

Cross symbolizing the Eucharist
Creative Commons Attribution Share AlikeCross symbolizing the Eucharist - Credit: Tom Orr

At Holy Communion, worshippers receive consecrated wine and bread (in the form of the communion wafer) as a signification of divine grace. Controversy, however, has raged around differing perceptions of what actually takes place here. To Catholics, who hold to the doctrine of transubstantiation, the bread and wine are literally the body and blood of Christ. Puritans, on the other hand, believe that Christ’s presence in these sacraments is of a spiritual nature. Their communions downplayed the sacrificial, and indeed cannibalistic, elements of the ritual, suggesting that it is perhaps these things which Dimmesdale has to prevent himself from speaking out loud.

A blasphemous reimagining of the Last Supper
Public DomainA blasphemous reimagining of the Last Supper - Credit: The Zatan Wikipedia