[quote="Paul_theApostle, post:1, topic:314451"]
Corinthians 1 ch 5-
Don’t you know that a little yeast leavens the whole batch of dough? 7 Get rid of the old yeast, so that you may be a new unleavened batch—as you really are. For Christ, our Passover lamb, has been sacrificed. 8 Therefore let us keep the Festival, not with the old bread leavened with malice and wickedness, but with the unleavened bread of sincerity and truth.**
Does this verse have anything to do with why the C. church uses Unleavened bread in the Mass compared to using leavened bread?
A little history of the leavened/unleavened bread is in order methinks.
It is most likely that in very early ages, most churches may have not originally thought of reproducing "unleavened bread," nor would they have that much opportunity or time to do so. Instead, they used ordinary bread that can be bought off at the local bakery. We do not know exactly when the West started to shift from (leavened) ordinary table loaf to a special unleavened bread. While many believed that it was an apostolic custom, St. Ambrose in De Sacramentis (4.4.14), supported by a sermon of St. Augustine, makes it certain that in the late 4th century the West was still using leavened bread.
Alcuin of York (writing in 798) is our first explicit reference to the use of azyma, but his reference does not suggest that in his time it was a recent innovation. Another actual definitive evidence we have of the West using azymes in the 9th century is Rabanus Maurus' strong statements in favor of unleavened bread in his de Institutione Christiana. The reasons for the shift to unleavened bread is unclear, but it may have been for practical reasons: unleavened bread left little to no falling crumbs and did not go putrid immediately, making it easier to reserve for the sick. The use of unleavened bread may indeed have been intended to mark off eucharistic bread from ordinary bread as something special.
Once unleavened bread was introduced, a powerful symbolism attached to it, and those words of St. Paul did find a new resonance - all the more since the Latin text has "Do you not know that a little leaven corrupts (corrumpit) the whole dough?" Two systems of symbolism, focused on the same liturgical act, developed, but they took their inspiration from the stark contradiction of leavened or unleavened bread.
The refusal, on either side, to enter the symbolic world of the other could be presented as a fundamental apostasy. The Latins, with their unleavened bread, are being Judaizers and on top of that, Apollinarianists (i.e. denying the full humanity of Christ); the Byzantines, with their leavened bread, are were virtual Marcionites, discarding the Old Covenant, and rejecting Christ's fulfilment of said covenant by celebrating the Passover with His disciples. There is also the fact that the Byzantines understood the Eucharistic bread to be necessarily consubstantial with humanity, while the Latins emphasized its "supersubtantiality," its otherworldliness. For the Byzantines, the use of ordinary bread, identical with the bread used as everyday food, was the sign of true Incarnation: it was considered to be a powerful symbol of Jesus "becoming flesh and dwelling among us."
At the time this controversy erupted, there was another group of Christians which were using unleavened bread as well: the Armenians. The Byzantines perceived that the use of unleavened bread and pure wine (contrary to the custom of most of Christendom, which mixes water with the wine) by the Armenians - who disagree with the dyophysite formula defined by the Council of Chalcedon - were akin to a rejection of the Chalcedonian idea of Jesus having two natures. (It seems, though, that the Armenian practice may actually predate the council, and this connection is only incidental.) Before the Latins, the Byzantines were already attempting to 'correct' the Armenians, to no avail - in fact, most of the arguments levelled against the Latin use of unleavened bread were recycled from polemics aimed against Armenians.