This is something that I have been looking into over the last decade. For Protestants, this is not a vitally important matter, except that some people put great store in celebrating an authentic Passover meal in the context of communion, when it seems it wasn’t any such thing.  But for Catholics, it is another matter, being tightly bound up in their doctrine of the Mass.

Having gone through the exercise of writing a chronology of the events of the days around Jesus death and resurrection in https://amos.gs/blog/2020/10/jesus-death-and-resurrection-sequence-of-events/, I thought I would also document a list of arguments as to why the Last Supper should not be considered to be a Passover (Seder) meal:

1. Bread

The Greek word for bread used in Luke 22:19 (and parallel passages), is ἄρτος (artós), the word commonly used for bread.  Strong’s Concordance says that this word is derived from the word to raise (αἴρω airō) – it is bread with a raising agent – leavened.  It is not the word for unleavened bread ἄζυμος (azumós), which is used in Luke 22:1 to describe the feast of unleavened (bread).  By the way, In Greek, it is common to leave the noun out, which the translators into English then have to supply, because it sounds strange in English, so we might assume from the translation that “artos” is used here too, but it is not.

They eat unleavened bread during the actual Passover meal, as specified in Exodus 12:8, where the Hebrew is מַצָּה (matza).

In the 3rd to 2nd centuries BC, the Jewish community in Egypt translated the Old Testament into Greek, as that was the common language in the area, thanks to Alexander the Great and his successors.  This translation is called the Septuagint¹ (LXX for short) as the number 70 is involved in stories of its history.

Incidentally, it is this version of the OT that the NT writers (who were writing in Greek), often use when  they quote the OT.

Why bring this up?  Well the LXX translates Ex 12:8 as as ἄζυμος (azumós) (unleavened), again assuming the noun.  The word for bread, artos is not used.

This means that when the NT writers used the word artos, they are unlikely to be referring to unleavened bread.  They don’t use the word azumos there, which is surprising if it was unleavened, as that is a major part of the symbolism of the Passover meal.  This includes Paul and his usage in 1 Cor 11:23.  Paul just uses the word artos, with no reference to it being unleavened.

It is true that the word artos is used in the context of unleavened bread in Ex 29:2.  The noun is supplied there because the passage is talking about three unleavened items: bread, cakes and wafers, so they need to be specific.  But here artos is used with the adjective.  It seems that Greek usage is like English.  If we refer to bread, we know that leavened bread is meant, unless we add the adjective “unleavened” to it.  Again, this points towards the understanding that the Last Supper was a Passover meal.

I don’t know anything about the group calling themselves “Hope of Israel Ministries”. But their take on all this confirms my own⁴:

Now the word for “bread” in all these verses is the Greek word artos, which means a “loaf of bread,” that is, a raised loaf, or leavened bread. The Greek word used when normally speaking of “unleavened” bread is azumos, which means “unleavened.” But the word artos generally refers to regular, normal, leavened bread — the kind we eat throughout the year! Regular loaves of bread were “leavened.” Yeshua himself spoke of the “leaven of bread [artos]” (see Matt. 15:12). Whenever ‘unleavened” bread is mentioned in the New Testament, the word used is always a totally different word — azumos (for example, see Matt. 26:17; Mark 14;1,12; Luke 22:1,7; Acts 12:3; Acts 20:6; I Cor. 5:8).

2. Showbread

Some would dispute this assertion by pointing out that the word artos is used for the showbread in the temple.  They claim that showbread was unleavened, so artos includes unleavened bread.

However there is some dispute whether the showbread was unleavened or not.

The term is used in 1 Chronicles 23:29 where it is distinguished from the “unleavened wafers”.  The word for unleavened (azumos) is not used with artos, so, the argument goes, if showbread is always unleavened, then artos can mean unleavened.

Where do they get the idea that the showbread is unleavened?

In the first century AD there was a Jewish historian called Josephus.  He says that the show bread was unleavened bread².

However Josephus is (in my limited experience) rather unreliable, and makes up things wherever it suits him.  

One example is his saying that John the Baptist was imprisoned at Macherus, a prison east of the Dead Sea. However, that doesn’t seem to line up with the Gospel accounts of John being readily available at Tiberius for him to be beheaded.  Maybe John was imprisoned there for a while and then moved back to TIberius, but maybe not.

Another example is Josephus’ fictitious speeches given at Masada.  All who heard the speeches died in a mass suicide, so how could he know what they said?

This low view of Josephus is echoed by Andrew Steinman who comments “when using Josephus we must exercise caution, since it is well documented that he was not always accurate in his portrayal of events.”³

Now, it may well be true that in Josephus’ day, they did use unleavened bread for the showbread, but it doesn’t mean that it always had been.

My take on 1 Chr 23:29 is that again they are using artos for normal (raised) bread, and using the word unleavened (azumos) for the wafers, to be specific that they were indeed unleavened.

3. Last Supper

The term itself points to the idea of what the meal was – the last eating of leavened bread before the feast proper began. It was so much a part of what they did, that Matthew could refer to it as the “first day of the feast” (Matt 26:17).  It was part of the “Preparation” for Passover, hence that word is used to describe what the disciples were to do when getting ready for Passover.  See Mark 14:12, 16.

This is what the Israelites were instructed to do in Exodus 12:15 – “On the first day you shall remove leaven out of your houses”.

4. Roman Catholic versus Orthodox and Protestant Doctrine

This understanding of the Last Supper using leavened bread is also attested to in the Lexham Bible Dictionary, which notes that the Roman usage of unleavened bread “was in contrast to the earlier tradition of using a leavened loaf (Ἄρτος, Artos) in the Eucharist, maintained by the Orthodox Churches and revived by Protestant traditions.”

It describes how the Council of Trent reaffirmed the Roman view that only unleavened bread should be used in the mass, in opposition to the Reformer’s views.  

The identification of the Last Supper and hence the Mass with the Passover is important for their doctrine of re-sacrificing Jesus at the Mass.  The Roman emphasis on the use of unleavened bread flows from this⁵.

This idea is backed up by the rubrics (notes) in the 1662 Book of Common Prayer of the Anglican Church, which specify:

And to take away all occasion of dissension, and superstition, which any person hath or might have concerning the Bread and Wine, it shall suffice that the Bread be such as is usual to be eaten; but the best and purest Wheat Bread that conveniently may be gotten.⁸

The bread that is “usual to be eaten” is, of course, leavened.

5. Brethren Church Doctrine

This view of the Last Supper is argued for in the The International Standard Bible Encyclopaedia in a section titled “The Last Supper Was Not the Jewish Passover”, written by D. W. Kurtz.  Describing the views of the Brethren Church, he refers to the way John describes the events of that evening, but adds to that⁶:

1. ‘Christ died at the time the Passover lamb was slain on Friday afternoon, the 14th of Nisan, and thus became Our Passover (1 Cor 5:7), “For our passover also hath been sacrificed, even Christ.”’
2. ‘Jesus, the “Lamb of God” (Jn 1:29) corresponds to the Passover lamb (Ex 12:3).’
3. ‘Jesus arose the third day and became “the first-fruits of them that are asleep” (1 Cor 15:4, 20, 23). The resurrection was on the first day of the week. The sheaf, or first-fruits, was gathered on the 16th of Nisan. Therefore Jesus must have died on Friday the 14th of Nisan, when the Passover lamb was slain; hence after the Last Supper.’
4. ‘All the early traditions, both Jewish and Christian, agree that Jesus was crucified on the day of Preparation of the Passover, and they distinguish between the Passover and the Last Supper which was eaten the evening before the Jewish feast.’

6. Don Carson

In The Gospel according to John⁷, D. A. Carson, in discussing this issue, notes that another commentator “France argues that John’s chronology is right, and that the Synoptics do not contradict it. What Jesus ate was not the Passover but a meal that anticipated Passover, since he knew that at the time of the Passover he would be hanging on the cross.”   At least France agrees with me!

Carson seems to be using a different year for the Crucifixion than the one I use above, stating that “In that particular year, the Passover ran from about 6:00 p. m. Thursday to about 6:00 p. m. Friday.”  He doesn’t seem to identify which year he is referring to.  

Carson himself takes the view that the Last Supper was indeed a Passover meal and attempts to align John’s Gospel with that view as he goes through.  In order to achieve this, for example, he assumes that the foot washing occurred the evening before, rather than being part of the Last Supper, so the Last Supper can then be on the succeeding evening and be a Passover meal.  Of course there is no clue in the text that this is what John meant!

Personally I don’t think the question is as complex to resolve as Carson makes out.

Notes:

1. https://www.britannica.com/topic/Septuagint
2. https://biblehandbookidea.wordpress.com/showbread-bread-of-presence/
3. When Did Herod the Great Reign? Steinmann, Andrew E., Novum Testamentum, Volume 51, Number 1, 2009 , pp. 1-29(29).  Available online at: http://www.jstor.org/stable/25442624
4. http://hope-of-israel.org/showbred.htm
5. Gibson, S. (2016). Douay Version. In J. D. Barry, D. Bomar, D. R. Brown, R. Klippenstein, D. Mangum, C. Sinclair Wolcott, … W. Widder (Eds.), The Lexham Bible Dictionary. Bellingham, WA: Lexham Press.
6. Gummey, H. R., Dosker, H. E., Dau, W. H. T., & Kurtz, D. W. (1915). Lord’s Supper, Eucharist. In J. Orr, J. L. Nuelsen, E. Y. Mullins, & M. O. Evans (Eds.), The International Standard Bible Encyclopaedia (Vol. 1–5, p. 1928). Chicago: The Howard-Severance Company.
7. Carson, D. A. (1991). The Gospel according to John (p. 456). Leicester, England; Grand Rapids, MI: Inter-Varsity Press; W.B. Eerdmans.
8. http://justus.anglican.org/resources/bcp/1662/HC.pdf