[quote="MarkThompson, post:16, topic:273292"]
The best evidence, though, is that Christ used unleavened bread (see, e.g., Mt. 26:17: "And on the first day of the Azymes ..."), that unleavened bread was originally used throughout the entire Church, that over the next couple of centuries the use of leavened bread gradually spread, and the the eastern portions of the Church simply never reverted to the older practice.
What we can find is that leavened has always been used. It is possible that there is an indifference with the use of leavened or unleavened in the first few centuries of the Church. Perhaps the Apostles were simply instructed to use bread, and they saw the use of unleavened bread during the Last Supper as incidental rather than a Sacramental necessity.
[quote="figs, post:17, topic:273292"]
Ok, help me understand, please.
The first communion (last supper) was with unleaven bread (passover meal)
when did it change to leaven bread?
On the contrary, evidence is that the Churches used leavened bread early on and it changed to unleavened for some later on. One theory is that the Apostles and Early Church Fathers used bread, regardless if its leavened or unleavened.
Remember that the Apostles were commanded by Christ to travel light, bring nothing. They lived off the communities they visited. So they would not have brought supplies of bread with them for the Commemoration, but rather will use whatever bread is available at the town/city they visit. I'm not sure what the availability of leavened vs. unleavened at that time in various cities around the Mediterranean but its quite possible that leavened bread may just be more available in some locations than in others.