Question:
Why is it that unleavened bread is not used at the remembrance meeting?

Answer:
When the Lord instituted in remembrance of Himself, what we call the Remembrance Feast or “the Lord’s Supper,” as it is called in 1 Corinthians 11:20, He took bread as a symbol of His body which He gave for us. The bread He used was unleavened since that type of bread was required for the Passover by the law of Moses.

However, when the truth of the Lord’s Supper was revealed to Paul by the Lord, unleavened bread was not mentioned, nor commanded; but just ordinary bread (verses 23 & 24). Whether or not the disciples in the early church used unleavened bread in their remembrance of the Lord is not known from Scripture. They could have used the more commonly available yeast-raised bread just as well.
But if we wish to be guided by the symbolism of Scripture concerning leavened bread, then 1 Corinthians 10:16, 17 is most important. According to these verses the “bread which we break” has a double symbolism. It is a symbol both of Christ’s human body and His spiritual body. He suffered the death of the cross (oh, how He suffered!) in His human body. All true believers know something (how little!) about this. And there is now on earth His body, the Church. “For we being many are one bread [loaf], and one body; for we all are partakers of that one bread [loaf].” Christ has one testimony to Himself on earth. It is His body, the Church, of which every true believer is a member, and in whom sin still dwells, but who “have crucified the flesh with the affections and lusts” (Galatians 5:24). When partaking of the loaf we, in addition to remembering the Lord, are testifying to the unity of His body, the Church, on earth. “For we all are partakers of that one bread [loaf].” The word “loaf” is better than “bread” because it is such an excellent symbol of unity. And the unity depicted in the loaf is that of Christ AND His Church, for it is His body. Just as the Church cannot be divided so the body cannot be severed from its Head. This is even true in spite of the Church’s fragmented testimony to Christ. When we see this truth we realize how appropriate a symbol is bread baked with leaven for use in the Remembrance Meeting since our sinless Lord and Savior will ever be one with His Church.