Though not in Aleppo’s list, Exo. 12:2 gives some additional important information for understanding the timing of the Passover. Again, being literal to get the flavor of the Hebrew text: Exodus 12:1
YHWH said to Moses and Aaron in the land of Egypt Exodus 12:2
"This moon הַחֹ֧דֶשׁ (ha-codesh) shall be for you the head (beginning) רֹ֣אשׁ (rosh) of moons חֳדָשִׁ֑ים (codeshim); the first/chief ( רִאשׁ֥וֹן ; rishun) this to you (plural) for the moons of the year ( לְחָדְשֵׁ֖י הַשָּׁנָֽה ; le-chodshē hash-shanah).
Here a yearly timing is indicated, that is, some number of moons that eventually return to the one at the head and that then repeat the cycle. For both the Gregorian and Julian calendars a year is 12 calendar months and 365 days or, for leap years, 366 days. A year based on moons, lunar months, is 12x29.5 days = 354 day, 11 days short of the 365 day year. Basically every three years, the 12 lunar months fall behind by 3x11 days=33 days, thus 3 or 4 days more than a lunar cycle. When this happens, the Hebrew calendar must add an additional month, a leap month, to insure that the calendar is synchronized with nature. More than being just a page of a yearly wall calendar, the lunar month, the cycle of the moon, is a natural, celestial event. The calendar’s job is to accommodate the event. Nature determines and dictates the timing; calendars are just overlays on the natural, cosmic timing.
From Aleppo’s list, Lev 23:5 conveys the same basic instruction as Exo. 12:8, but with a refinement:Leviticus 23:5
At the moon (חֹדֶשׁ ), the first/head, on the fourteenth for the moon ( לַחֹ֖דֶשׁ ) between the evenings ( הָעַרְבָּ֑יִם ) is the Pesach/Passover ( פֶּ֖סַח) to YHWH ( לַיהוָֽה ).
The time specified is not just evening as in Exodus but more specifically ha-arbaim, between the evenings, which is believed to be the time between noon and the evening twilight that begins the 14th day. But is it, is that the meaning?
The verses in Numbers give important additional information, relating the 14th and the 15th days: Numbers 28:16
"On the fourteenth day of the first moon ( הָרִאשׁ֗וֹן ) is the YHWH's passover. 17 And on the fifteenth day of this moon is a feast; seven days shall unleavens be eaten.
In these translations, first has the meaning of primary rather than an ordinal number. So, the Passover is on the 14th and the meal is on the 15th, recalling that this is the evening-and-morning biblical day.
Exactly when, however, does this moon that corresponds to the moon at the time of the Exodus, the moon that is at the head of all the moons throughout the year occur? This is an example of that liturgical today. For every year, for every generation after the actual exodus from Egypt, the same participation in the actual event is realized by the timing of the moon and sun. Every year the timing of the event is replicated by the specified day of the moon, of the designated moon of the year, not by giving a date on a calendar, but in compliance with the present timing of nature, of the earth, moon and sun. This is the moon of YHWH's Passover made present, today, for every generation.
The specified moon is given in Deuteronomy & Exodus:Deuteronomy 16:1
"Observe the moon of Aviv ( חֹ֣דֶשׁ הָאָבִ֔יב ; chodesh ha-Aviv) and keep the פֶּ֛סַח Pesach/Passover to YHWH your God; for in the moon of Aviv, YHWH your God brought you out of Egypt by night. 2 And you shall slaughter Pesach/Passover פֶּ֛סַח to YHWH your God, …Exodus 13:1
YHWH said to Moses, 2 "Consecrate to me all the first-born; whatever is the first to open the womb among the people of Israel, both of man and of beast, is mine." 3 And Moses said to the people, "Remember ( זָכ֞וֹר zachor; μνημονεύετε , mnemoneuete) this day, in which you came out from Egypt, out of the house of bondage, for by strength of hand YHWH brought you out from this place; no leavenes shall be eaten. 4 This day you are to go forth, in the moon of Aviv.Exodus 23:15
You shall keep the feast of unleavens ( חַ֣ג הַמַּצּוֹת chag_ham-matstsot; ἑορτὴν τῶν ἀζύμων); as I commanded you, you shall eat unleavens for seven days at the appointed time ( לְמוֹעֵד ; le-moed) in the moon of Aviv, for in it you came out of Egypt…
Thus the time of the Exodus, the appointed time (the feast) of Pesach/Passover and Unleavened Bread (I have not translated it this way since there is no explicit word bread) is the moon of Aviv (This moon of Aviv also goes by its Babylonian name, Adar). Aviv in OT Hebrew means the new, not fully ripened, green barley [Cf. LXX: ἐν μηνὶ τῶν νέων (Exo 13:4)]. This phenomenon of nature occurs in the spring and gives the solar, the seasonal timing for the moed [at the appointed time ( לְמוֹעֵד ;le-moed)], the specific moon of the twelve (or thirteen) moons that return the yearly cycle to the season when the barley has appeared. (In modern Hebrew, Aviv actually means Spring; the modern city and former capital of the State of Israel, Tel Aviv, is Hill of Spring.)
It was important on a practical level to get the timing of this moon correct (See, Sacha Stern, Calendar and Community
, 70,"The year may be intercalated on three grounds..."). This is because there is an additional directive that ties Passover/Unleavended Bread with another important feast. It is important to get the Aviv Moon correct in order to make good on the availability of the Aviv, the barley, for the ritual offering of the Omer. This is recorded in the books of Leviticus and Deuteronomy: Leviticus 23:10
"Say to the people of Israel, When you come into the land which I give you and reap its harvest, you shall bring the sheaf עֹ֛מֶר (omer) of the first (fruit) רֵאשִׁ֥ית (rēshit, ἀπαρχὴν ) of your harvest to the priest; Leviticus 23:11
and he shall wave the sheaf before the YHWH, that you may find acceptance; on the morrow after the sabbath the priest shall wave it… Leviticus 23:15
"And you shall count from the morrow after the sabbath, from the day that you rought the omer of the wave offering; seven sabbaths שֶׁ֥בַע שַׁבָּת֖וֹת complete shall they be, Leviticus 23:16
counting fifty (LXX: πεντήκοντα) days to the morrow after the seventh sabbath; then you shall present a cereal offering of new grain to the YHWH. Deuteronomy 16:9
"You shall count seven weeks; begin to count the seven weeks from the time you first put the sickle to the standing grain. Deuteronomy 16:10 Then you shall keep the feast of weeks to the YHWH your God with the tribute of a freewill offering from your hand, which you shall give as the YHWH your God blesses you;
These verses account for the timing of Passover and Unleavened Bread and the Moed (appointed time, feast) of the first-fruit (omer) and its counting to the 50th day, the Moed called Shavuot (Hebrew: שָׁבוּעוֹת, Šāvūʿōṯ, lit. "Weeks") in the Hebrew text of scripture, and Pentecost in Greek. This is the Moed/feast that Luke describes in Acts: Acts 2:1
When the day of Pentecost had come, they [the disciples] were all together in one place. Acts 2:5 Now there were dwelling in Jerusalem Jews, devout men from every nation under heaven.
It must be noted, however, that while the timing, the linking of Passover and Unleavened Bread is explicit, the choice of the Sabbath and thus the "morrow after the sabbath" in the Leviticus passages is not explicit. This is true for Luke's account in Acts. Our liturgical year interprets that "morrow" as Pascha, and this was and is a common interpretation in Jewish practice also.
There is one last text concerning the preparation for the Passover, and it highlights an important aspect of our liturgical theology: Exodus 12:3
Tell the whole community of Israel that on the tenth day of this month each man is to take a lamb for his family, one for each household… Take care of them until the fourteenth day of the month, when all the members of the community of Israel must slaughter them at twilight. Exodus 12:6
and you shall keep it until the fourteenth day of this month, when the whole assembly of the congregation of Israel shall kill their lambs in the evening.
This 10th day, the day the lamb is selected, corresponds to the day that Jesus entered Jerusalem in triumph, the day observed liturgically as Palm/Flowery Sunday. This coincidence and its interpretation is discussed at some length by what I would characterize as non-liturgical Christian communities. I do not see it appearing in our (extensive) liturgical commentary, our prayers. Its link to the OT is not referenced in the NT. I wonder if this is noted at all in Patristic writings. The proper correspondence of OT feasts with our liturgical tradition, along with important cautions, is discussed by Fr. Sebastian Carnazzo, Rejoice All ye Peoples: The Feasts of the Old Testament
] at God With Us
, a presentation that I highly recommend.