In John 18:28, we have the example of the Jews. Both the Sadducees and the Pharisees had departed from the original Passover instructions; but they still considered eating the Passover as keeping it, even though they did not obey properly in regard to the time element. (They did it one day late.)
That is where the concern was—about whether they could eat it. And what irony there is here! They hated Jesus Christ. They were plotting and planning on killing Him. And yet they were so careful to be ceremonially clean so that they might eat the Passover. And, all they while, they were participating in killing the true Passover! What irony there is there!
