Please turn to I Corinthians 11. A large part of this letter is dedicated to a foundational ritual that was being observed incorrectly. Paul had to correct the congregation regarding the Passover, both in the details of the practice, as well as in their overall approach. If the Corinthians truly understood the Passover, it would have shaped their conduct for the better in numerous areas. But their present behavior showed Paul they weren't getting it yet.
Paul warns against participating in this annual practice in an unworthy manner, or we could say, in a manner that is not fitting or appropriate for the occasion. The manner in which we approach and observe the Passover is so important that Paul indicates that God had afflicted many in the congregation, and He had also either put many to death or at least allowed many to die. The fact that a ritual cannot justify or save does not mean it is unimportant. As this indicates, God is deadly serious about this service in particular.
The Corinthians were guilty of not fully appreciating the bread and wine, as proved by their gluttony and even drunkenness at the Passover meal. That is one way of observing the Passover in an unworthy manner. But we can similarly be guilty if we go through the Passover on autopilot - if we partake of the bread and wine without meditating on all that they stand for, such that the meaning is real, and personal, and changes us. So, today we will review the symbols of the bread and the wine so that when we observe the Passover, we can have a fitting appreciation of the depth and significance of these symbols in our minds.
Thus, even though the Passover is just a ritual, the way we approach it and observe it indicates to God what value we place on this covenantal relationship. Remember that God caused many to be sick and to die in Corinth because they were losing their appreciation for the Passover and what the symbols entail. This was manifest not only in the drunkenness, gluttony, and self-serving behavior at the Passover itself, but also throughout the year in their interactions. Our conduct and the state of our relationships in the body give evidence of what the bread and wine truly mean to us. The evidence cannot be hidden. A life in which these symbols hedge and guide every deed, word, and thought, will be quite different from a life where the relationship with God is on autopilot while other things are pursued.