The first reason is historical. The Seder ritual, as it is practiced today, did not exist at the time of Jesus. It was only fully developed by the rabbis in the years following the destruction of the Temple in 70 C.E., in other words, at least two generations after Jesus. Many assume that Jesus, at the Last Supper, conducted what we now know of as a traditional Passover Seder with the Pesakh (pascal) offering of the lamb, matza, bitter herbs, the telling of the tale of the Exodus from Egypt, and other rituals as found in the Jewish Passover Hagada. This is incorrect. To put it bluntly, Jesus certainly celebrated Passover, but neither he nor his disciples ever attended a Seder, any more than they drove a car or used a cell phone.
In the Last Supper, Jesus surely is making allusions to the Exodus, as does the Jewish Passover meal, but that event takes a back seat to his revealing himself as “the Passover lamb,” as the object of a new and revolutionary expression of faith. The Jewish Passover meal inaugurates the Jewish people into its history; it prepares them to fulfill the responsibilities of the mitzvot (commandments) given at Sinai. As such, it is an event designed for and limited to the Jewish people. Jesus of Nazareth, in the Last Supper, presents himself as the offering not just for all Israel, but for all of humanity. He is, in short, establishing a unique ritual. In our view, celebrating a Christian Seder to commemorate the Last Supper misses the point historically.
Second, adopting another’s ritual shows a lack of respect. Even when pursued with the best of intentions, taking another faith’s sacred ritual and transforming it into an expression of one’s own tradition displays a misunderstanding of the complex nature of faith traditions. Good relations between Christianity and Judaism, and by extension, other faiths as well, may begin with acknowledging common principles, but also demand a clear articulation of the profound differences that separate them. However, it is surely not the goal of good interfaith relations for Jews and Christians to co-opt or reshape one another’s rituals for their own ends.
On the other hand, for the Jew, the Passover Seder is not some quaint experience such as Thanksgiving dinner or a Fourth of July barbeque, which like other aspects of our American “civil religion,” Jews and Christians should and do share, readily and with ease. The Passover Seder expresses the belief that God who redeemed us once from Egypt will in the End of Days inaugurate the messianic era for the first time, redeem the Jewish people from the Exile in which we now find ourselves, and ultimately bring God’s eternal reign of peace and righteousness to the entire world. It is the meal that celebrates that Jews are God’s chosen people with a unique mission, and points back to what we believe is the first and only divine revelation, at Sinai.We like to think of rituals as the lovemaking between a faith community and God. They are unique, and they express utterly distinct beliefs that Jews and only Jews hold, or that Christians and only Christians hold. In our experience, Jews who encourage a Christian adaptation of the Passover Seder view and naturally emphasize Jesus as a fine teacher, partaking of the Jewish culture of his times, interested in the same kinds of Torah learning as the Perushim, the righteous Pharisees whose teachings are foundational to rabbinic, and therefore, contemporary, Judaism. In doing so, such Jews do not realize they are showing profound disrespect and lack of understanding of Christian faith in Jesus. For the Christian, Jesus is not merely one more interesting and inspiring member of the Jewish scholarly community of the first century. Jesus was certainly part of that world, but for the Christian, Jesus is God incarnate, the risen Christ. For the Christian, the blood of the new Lamb of God on the cross is what atones not only for sin, but also brings salvation and life eternal.