We are here to re-create, in abbreviated form, the events of an evening two thousand years ago, when Jesus and a small band of his followers met to observe the LORD's Passover in obedience to God's command through Moses.
Exod 12:14 This is a day you are to commemorate; for the generations to come you shall celebrate it as a festival to the LORD—a lasting ordinance.
As the disciples gather with Jesus to celebrate the Passover seder, they know that this night is different from all other nights. The liturgy reviews God's deliverance of Israel from slavery in Egypt. The participants eat bitter herbs to remind them of the bitterness of bondage and matzah (unleavened bread) to recall the haste of Israel's departure. It is not a somber occasion, though, for the evening has a festive atmosphere, with four cups of wine representing different aspects of divine intervention. The participants recite the exodus story, sing psalms, pray, and discuss the significance of God's grace.
On this particular Passover, though, Jesus will do things a little differently. He will take the matzah and the third cup of wine, and he will give them an additional significance that points to God's deliverance from another kind of bondage. At every Passover thereafter, his disciples will remember their physical redemption from slavery and their spiritual redemption from sin. This night is different from all other nights, even from other Passovers.
Nevertheless, Jesus must prepare them in at least one more way for what lies ahead. The apostles have heard his instruction first hand and have witnessed his numerous miracles. After his death, people will look to them for guidance. They will no longer just be disciples but teachers in their own right, responsible for many more people than ever took part in Jesus' earthly ministry. The temptation to capitalize on that role and to abuse their responsibility will be significant.
They have already exhibited an interest in position and power and, on several occasions, Jesus has had to adjust their priorities.
Matt 18:4 ...whoever humbles himself like [a] child is the greatest in the kingdom of heaven.
Matt 20:26b ...whoever wants to become great among you must be your servant[.]
Matt 23:12b ...whoever humbles himself will be exalted.
Earlier this same evening "a dispute arose among them as to which of them was considered to be greatest" (Luke 22:24). So here, at his last seder before the crucifixion, Jesus addresses the issue one more time.
John 13:4 ...he got up from the meal, took off his outer clothing, and wrapped a towel around his waist. 5 After that, he poured water into a basin and began to wash his disciples' feet, drying them with the towel that was wrapped around him.