Complex sentence: On the other hand, most Eastern Churches explicitly forbid the use of unleavened bread (Greek: "azymes") for Eucharist as pertaining to the Old Testament and allow only for bread with yeast, as a symbol of the New Covenant in Christ's blood.
Split into simpler sentences: On the other hand, most Eastern Churches explicitly forbid the use of unleavened bread (Greek: "azymes") for the Eucharist. Eastern Christians associate unleavened bread with the Old Testament and allow only for bread with yeast, as a symbol of the New Covenant in Christ's blood.