A-, without; 0,un, leaven), a name given by the Orthodox Eastern to the Western or Latin Church, because of the latter's use of unleavened bread in the Eucharist, a practice which arose in the 9th century and is also observed by Armenians and Maronites following the Jewish passover custom.
In memory of this the Israelites were for all time to eat unleavened bread (matzoth) for seven days, as well as keep the sacrifice of the Passover on the eve between the fourteenth and the fifteenth of Nisan.
The Orthodox Church strenuously maintains its point, arguing that the very name bread, the holiness of the mystery, and the example of Jesus and the early church alike, testify against the use of unleavened bread in this connexion.
It still remains possible therefore that the seven days' eating of unleavened bread (and bitter herbs) is an historical reminiscence of the incidents of the Exodus, where the normal commissariat did not begin until a week after the first exit.
The first month on the 14th day of the month is the Passover; the 15th day of this month shall be a feast; seven days unleavened bread to be eaten; first day a holy assembly with fire offering, two young bullocks and one lamb and seven firstling he-lambs without blemish, with appropriate meal offering and one he-goat for sin-offering; on the seventh day another hol assembly.
The paschal lamb is no longer eaten but represented by the shank bone of a lamb roasted in the ashes; unleavened bread and bitter herbs (haroseth) are eaten; four cups of wine are drunk before and after the repast, and a certain number of Psalms are recited.
The decree explains the filioque in a manner acceptable to the Greeks, but does not require them to insert the term in their symbol; it demands that celebrants follow the custom of their own church as to the employment of leavened or unleavened bread in the Eucharist.
The Passover was kept in the first month on the 14th day of the month at even in the wilderness of Sinai; but certain men, unclean by touching a dead body, asked what they should do; they were to keep it on the second month on the 14th day, eating it with unleavened bread and bitter herbs, leaving none of it until the morning, nor breaking a bone.
As a memorial of this you shall eat unleavened bread seven days, on the 14th day at eve until the 21st day at eve; when children shall ask what this service means, you shall say that it is the Passover of the Lord.
Lengerke recognized a double motive: the lamb for atonement, the unleavened bread as a trace of the haste of the early harvest.