My friend quotes from 1 Corinthians as his justification:
“Get rid of the old yeast, so that you may be a new unleavened batch—as you really are. For Messiah, our Passover lamb has been sacrificed. “Therefore let us keep the Festival [Passover], not with the old bread leavened with malice and wickedness, but with the unleavened bread (matzah) of sincerity and truth.” (1 Corinthians 5:7–8)
What some call "the Lord's Supper" as initiated by the Lord Jesus Christ was actually the Lord keeping the Passover as a Jew under the law.
And when the hour was come, he sat down, and the twelve apostles with him. And he said unto them, With desire I have desired to eat this Passover with you before I suffer: for I say unto you, I will not any more eat thereof, until it be fulfilled in the kingdom of God.
Ironically, the King James Version obscures the practice in the Book of Acts by the use of the word "Easter" for Passover.
And when he had apprehended him, he put him in prison, and delivered him to four quaternions of soldiers to keep him; intending after Easter to bring him forth to the people.
But what of this age? Is this a practice for us? I would say the Word is clear the answer is "no." And it is not only not given to us, we have no business practicing the Passover (or the Lord' Supper). 1 Corinthians is written to Jewish and Gentile believers in the Acts age. As we have continually seen in our studies, that was a condition unique to that age. The book itself addresses each group separately at times.
But after the Acts Age ended, Paul reveals to us the current plan of God: the dispensation of the Mystery. In this age, there is no more "middle wall of partition" between Jew and Gentile. There is no law to separate us. We are no longer "grafted in" to Israel (Rom 11), but we are part of the "one new man." To this group (espcially gentile believers) Paul writes:
And you, who were dead in trespasses and the uncircumcision of your flesh, God made alive together with him, having forgiven us all our trespasses, having canceled the bond which stood against us with its legal demands; this he set aside, nailing it to the cross. He disarmed the principalities and powers and made a public example of them, triumphing over them in him. Therefore let no one pass judgment on you in questions of food and drink or with regard to a festival [feast] or a new moon or a sabbath. These are only a shadow of what is to come; but the substance belongs to Christ.
The question remains: is it then optional for the believer? I believe, again, the answer must be "no." But why? What harm is it? I think the problem is two-fold:
1. It is a feast always meant for Israel alone because it is inextricably connected to her hope of being a kingdom of priests. It is my belief and contention that even in Acts Age only Jews observed it.
2. It is not a good witness for the current age. Paul is very clear in Ephesians and Colossians about the uniqueness of the current age and our hope. This hope has nothing to do with the earth or earthly promises. Our blessing are in the "far above the heavens."
Now I rejoice in my sufferings for your sake, and in my flesh I complete what is lacking in Christ’s afflictions for the sake of his body, that is, the church, of which I became a minister according to the divine office which was given to me for you, to make the word of God fully known, the mystery hidden for ages and generations but now made manifest to his saints. To them God chose to make known how great among the Gentiles are the riches of the glory of this mystery, which is Christ in you, the hope of glory. Him we proclaim, warning every man and teaching every man in all wisdom, that we may present every man mature in Christ. For this I toil, striving with all the energy which he mightily inspires within me.
Blessed be the God and Father of our Lord Jesus Christ, who has blessed us in Christ with every spiritual blessing in the heavenly places, 4 even as he chose us in him before the foundation of the world, that we should be holy and blameless before him.
And we note, as we have in other studies, Ephesians speaks about a plan from "before" the foundation of the ages (cp Eph 3). In the Acts age, we have truths revealed "from" the foundation of the ages (Rom 1:20; etc.).
Related: The New Covenant is for Israel alone.