I think you misunderstood my question.
I was not asking if the first day of Unleavened Bread was a holy day. I asked whether the first day of Unleavened Bread was a Sabbath day.
The first day of U.B can be practiced like a sabbath day but by definition, the sabbath day is always the seventh day.
I would avoid calling the first day of Unleavened Bread a sabbath day, unless the scripture calls it a sabbath day.
It is a much safer path to walk.
There are annual Sabbaths (John 19:31 refers to the 1st day of Feast of Unleavened Bread as a HIGH SABBATH).
John 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 an high day,) besought Pilate that their legs might be broken, and that they might be taken away.
Scriptures instructing us that the 15th day of the first month is first day of Feast of Unleavened Bread and is a holy convocation and no work is to be done. All of these are found in Leviticus, Exodus and Numbers. Three times we are told.
This is what we are seeing on Christ's passion, that at sundown the new day begins. Christ crucified on the 14th (a Wednesday) and at sundown on that Wednesday begins the 15th, the first day of Feast of Unleavened Bread. This day in this year is not the weekly Sabbath. The Jews know the Torah, and observe the Torah, and wanted Christ taken down before the sun sets because
#1) the High Sabbath was upon them, and
#2) Deu_21:23
His body shall not remain all night upon the tree, but thou shalt in any wise bury him that day; (for he that is hanged is accursed of God
that thy land be not defiled, which the LORD thy God giveth thee for an inheritance.
Gal_3:13 Christ hath redeemed us from the curse of the law, being made a curse for us: for it is written,
Cursed is every one that hangeth on a tree:
Lev 23:4 These are the feasts of the LORD, even holy convocations, which ye shall proclaim in their seasons.
Lev 23:5 In the fourteenth day of the first month at even is the LORD'S passover.
Lev 23:6 And on
the fifteenth day of the same month is the
feast of unleavened bread unto the LORD: seven days ye must eat unleavened bread.
Lev 23:7
In the first day ye shall have an holy convocation: ye shall do no servile work therein.
Exo 12:15 Seven days shall ye eat unleavened bread; even the first day ye shall put away leaven out of your houses: for whosoever eateth leavened bread from the first day until the seventh day, that soul shall be cut off from Israel.
Exo 12:16
And in the first day there shall be an holy convocation, and in the seventh day there shall be an holy convocation to you; no manner of work shall be done in them, save that which every man must eat, that only may be done of you.
Exo 12:17 And ye shall observe the feast of unleavened bread; for in this selfsame day have I brought your armies out of the land of Egypt: therefore shall ye observe this day in your generations by an ordinance for ever.
Num 28:16 And in the fourteenth day of the first month is the passover of the LORD.
Num 28:17 And in the fifteenth day of this month is the feast: seven days shall unleavened bread be eaten.
Num 28:18
In the first day shall be an holy convocation; ye shall do no manner of servile work therein:
Weekly Sabbath = Leviticus 23:3 Six days shall work be done: but the seventh day is the sabbath of rest,
an holy convocation; ye shall do no work therein: it is the sabbath of the LORD in all your dwellings.