The icon of the Last Supper depicts the original Holy Eucharist when “Jesus took bread, and blessed, and broke it, and gave it to the disciples and said, ‘Take, eat; this is my body.’ And he took a cup, and when he had given thanks he gave it to them, saying, ‘Drink of it, all of you; for this is my blood of the new covenant, which is poured out for many for the forgiveness of sins.’” Mt. 26:26-28. “For as often as you eat this bread and drink the cup, you proclaim the Lord’s death until he comes.” 1 Cor. 11:26.
Because Jesus said, “this is my body…this is my blood,” Orthodox believe that the elements of bread and wine prepared for the Eucharist become the very Body and very Blood of Christ. That is why receiving the Eucharist, or Holy Communion, is not to be taken lightly. It is reserved for those confirmed in the Orthodox Faith, who have also prepared themselves by being at peace with everyone, and with prayer, fasting, and a recent confession.
Please read this compelling, yet brief, description of Divine Liturgy (the celebration of the Holy Eucharist) titled, Appreciating the Rhythms of the Divine Litugy, by Dr. David Carlson.