Pesachim 108 - Drinking wine and eating matzah
At the Seder, one is going to drink four cups of wine and eat good quantities of matzah. To prepare for this, Rabbah would drink wine all day. Rava, his student, explained: "How do we know that wine makes one hungry? - Because of the rule that between the first three cups of wine one can drink more, should he so desire. Now, if wine makes one satiated, this should not have been allowed, for then he would not eat matzah with appetite. It must be that wine makes one hungry."
Rav Yosef, on the other hand, would fast before the Seder. Why was he doing this? Could it be that he combined two opinions: that one should not eat or drink before the afternoon prayer (Minchah), and this is pushed back even earlier because of the Passover sacrifice? This would be an unusual opinion! - Rather, Rav Yosef was a very sensitive man, and had he eaten anything that day, he would not have enjoyed matzah to the fullest.
Reclining while eating was considered a sign of a free person, while slaves ate in a hurry, barely sitting down. Therefore, to signify that on that day we are becoming free, all participants in the Seder must recline while eating matzah and drinking wine. Some say that they must recline while drinking the first two cups, because then the beginning of freedom is discussed, while others claim that they must recline during the last two cups, when reading in the Haggadah about real freedom, whereas at the beginning of Exodus freedom was just a promise. To satisfy both opinions, people recline while drinking all four cups.
The wine, even if diluted, should have the taste and appearance of wine. One could even drink all four cups at once, though he would not have fulfilled the mitzvah with all its details.
Art: Still Life of Glass Goblet by Pieter Claesz