Well, you found a good source for the fact that the Jews celebrate the Passover on the 15th, following the tradition of the Sanhedrin, but that there was biblical reason for Christ having his passover a day earlier, on the 14th.
But here’s the thing: You still haven’t shown where the bible calls the Feast of the Unleavened Bread a Sabbath. And even if it were, that would only make it more unbelievable that an event which happened on a Saturday AFTER such a Sabbath would be said to have happened “on the first of the Sabbaths.”
You may say to yourself “a holy convocation with no labor... isn’t that a Sabbath?” You’d be wrong. Sabbath comes from the Jewish word, Shabot. The word for “Seven” is Shabiyiy. The Sabbath is the seventh day. Hence, the SEVENTH day of the Feast of Unleavened Bread is a Sabbath. The first day is not. Notice the word, “shabbath” (”rest”) isn’t used to describe the lack of labor, lest the Shabbath be confused with a Shabot. (Yes, the words are related.)
Consider this language, used in Leviticus, after establishing these feast days (also including Penteocost, Rosh Hashannah, Yom Kippur, etc:)
“These the feasts of the LORD, which ye shall proclaim holy convocations [Miqra] , to offer an offering made by fire unto the LORD, a burnt offering, and a meat offering, a sacrifice, and drink offerings, every thing upon his day:
beside the sabbaths of the LORD, and beside your gifts, and beside all your vows, and beside all your freewill offerings, which ye give unto the LORD”
See, these days are called “Miqra,” and they are to be given to the Lord BESIDES the Sabbaths, gifts, vows, etc.
>> Christ died on Passover, which is not a sabbath. But the first day of unleavened bread IS a high holy day. <<
No, the lamb is slaughtered the day BEFORE Passover. The ambiguity of Leviticus (the Jews take Lev 23:5 to mean that the Passover starts at the evening of the 14th) permitted Christ to have himself sacrificed as the Paschal lamb AFTER sharing the passover meal with his disciples.
First of all you're correct. The first day of unleavened bread is never technically called a "sabbath" in Leviticus 23. It is, as you've pointed out, a commanded day of worship and a day of no servile work. However, other holy days (atonement, trumpets) are specifically called sabbaths. By nt times (apparently) the other feast days have come to be called annual sabbaths, or high sabbaths, to distinguish them from the weekly sabbaths.
Joh 19:14 And it was the preparation of the passover, and about the sixth hour: and he saith unto the Jews, Behold your King!
Joh 19:31 The Jews therefore, because it was the preparation, that the bodies should not remain upon the cross on the sabbath day, (for that sabbath day was a high day,) besought Pilate that their legs might be broken, and that they might be taken away.
But I'm not sure what the point is in drawing the distinction?
And even if it were, that would only make it more unbelievable that an event which happened on a Saturday AFTER such a Sabbath would be said to have happened “on the first of the Sabbaths.”
As Diego pointed out (I believe) "first of the sabbaths" refers to the count of 7 sabbaths (or 7 weeks of sabbaths) used to determine Pentecost. To be fair, those who observe God's holy days DO have a difference of opinion on when to start this count and thus disagree on when to observe Pentecost. But THAT'S a thread all by itself. :-)