פירוש על דברים 16:8

ששת ימים תאכל מצות SIX DAYS THOU SHALT EAT UNLEAVENED BREAD — But in another passage it states, (Exodus 12:15): “seven days [ye shall eat unleavened bread]’’! But the explanation is: seven days ye may eat Mazzoth prepared from the old produce and six days (out of the seven. i.e. the last six days, after the Omer has been offered and the new crop has become permitted as food) ye may eat Mazzoth prepared from the new crop (Sifrei Devarim 134:5). Another explanation is: It teaches regarding the eating of unleavened bread on the seventh day of Passover that it is not obligatory; and from here (from this law concerning the seventh day) you may derive the law for the other six days. For the seventh day was included in the general statement (“seven days, thou shalt eat unleavened bread’’), and in the text: “six days thou shall eat unleavened bread” it has left the general statement, to teach ... eating unleavened bread on it is not obligatory but optional. Now, according to the well-known rule, it did not leave the general statement in order to teach this regarding itself alone but regarding everything that is included in the general statement. Now how is it with the seventh day? It is optional as regards the eating of unleavened bread (as explained in the earlier portion of this comment)! This, too, according to the rule, applies also to everything that was included in the general statement, and therefore all the other days are also optional in this respect, with the exception, however, of the first night of Passover, for which Scripture has fixed it (the eating of unleavened bread) as an obligation, as it is said, (Exodus 22:18) “at evening ye shall eat unleavened bread” (Pesachim 120a; cf. also Rashi on Exodus 12:15).

Now he said, And on the seventh day [of Passover] shall be a solemn assembly to the Eternal thy G-d; thou shalt do no work therein.³⁴⁸Verse 8. But he did not mention the prohibition of work on the first day [of Passover]; he likewise did not state such a prohibition for the Festival of Weeks, nor for Tabernacles, nor did he mention the commandment of the palm-branch [on the Festival of Tabernacles] and he likewise did not mention here the Day of Remembrance [i.e., the New Year] and the tenth of that month [i.e., the Day of Atonement] — the reason, as I have explained, is that now he came to mention only the [commandment to make an] appearance [in the Sanctuary] and the [commandment of] festivity, for all Israelites are obligated to make a pilgrimage on these three festivals to the place which G-d shall choose and celebrate there every man as he is able, according to the blessing of G-d which He hath given him,³⁴⁹Verse 17. to rejoice before Him, to thank for all the good which He hath bestowed on us according to his compassions, and according to the multitude of His mercies.³⁵⁰Isaiah 63:7.
He [Moses] added, and on the seventh day shall be a solemn assembly³⁴⁸Verse 8. meaning: Six days thou shalt eat unleavened bread³⁴⁸Verse 8. and in addition to them is a solemn assembly on the seventh day, the purport being that they be further detained before Him to eat the unleavened bread. And because he said that [the seventh day] is Atzereth it might possibly mean that they be “restrained” only for the eating of the unleavened bread as on the [six] preceding days, therefore it was necessary to admonish [also in the same verse] that you are not to do work therein. Similarly He said with reference to the eighth day of the Festival of Tabernacles in the section on the festivals in the Book of Leviticus, Seven days ye shall bring an offering made by fire unto the Eternal; on the eighth day shall be a holy convocation unto you; and ye shall bring an offering made by fire unto the Eternal; it is a solemn assembly; ye shall do no manner of servile work,³⁵¹Leviticus 23:36. meaning that [the eighth day] is restrained in addition to the first [seven] days with respect to the bringing of a fire-offering, and it has a further prohibition against [doing therein any manner of] servile work, [a prohibition shared only by the first day of Tabernacles, but not by any of the intermediate days].
And by way of the Truth, [the mystic teachings of the Cabala, the verse stating that the seventh day of Passover] Atzereth³⁴⁸Verse 8. is “the congregation of Israel,”³⁵²Here used as a Cabalistic term, alluding to the first seven Emanations. and the verse comes to each us the secret of the day. But it is not like Atzereth of the eighth day of Tabernacles, for the eighth day is a separate festival³⁵³Rosh Hashanah 4b. See Ramban to Leviticus 23:36 (Vol. III, pp. 392-394). and the offering brought then, is for the congregation of Israel, but it is unlike the offerings brought on the seven days [of the Tabernacles]. The seventh day of Passover, however, is part of the Festival [of Passover] and it is Atzereth, for, sometimes it is counted as the eighth³⁵⁴See Vol. I, p. 27, Note 64. It is thus considered “eighth” if the count of the Emanations begins with Kether (crown). See L’vush Ha’orah to Ricanti here. and sometimes it is included [as part of the seven]. Thus it is like the Sabbath in which there is the [commandment to] remember and [the commandment to] observe, the honor for the day and honor for the night.³⁵⁵See Vol. II, pp. 308-309. [Thus the offering on the seventh day of Passover is part of the festival], and therefore he said here, a solemn assembly to the Eternal thy G-d, while there [with reference to the eighth day of Tabernacles] it is said, and ye shall bring an offering made by fire unto the Eternal; it is a solemn assembly,³⁵¹Leviticus 23:36. meaning that the offering is the Atzereth and therefore “the meal” is small.³⁵⁶This is a reference to the fact that the Additional Offering on the eighth day of Tabernacles was smaller than those of the preceding seven days, and also smaller than the Additional Offering of the seventh day of Passover. The student learned in the mystic teachings of Cabala will understand.
He [Moses] did not mention here the eighth day of the Festival of Tabernacles, because it has already been mentioned, and [because] there is no obligation that we go up in pilgrimage to the Sanctuary another time [in honor of the eighth day].

וביום השביעי עצרת, on that day the Israelites are to be assembled together in communal worship of the Lord. They will sing the song sung by the Israelites after they had crossed the Sea of Reeds on dry ground. This is why this day has been given a special sanctity.