Translation:Arukh ha-Shulchan/Orach Chaim/429
'Nisan' is the head of all the months. This is due to its great stature, even though the counting of years begins with the month of 'Tishrei'. This is based on the verse that states [Shmos, 12.1]: "This month should be for you the head of all the months, it is the first of all the months of the year." The intent of this verse is that the month is considered the 'head' of all the months, and there it has the distinction of being counted as the first when the months are enumerated.
What then is the source of this 'great stature'? It is the exodus from Egypt, which occurred in this month and demonstrated the existence of the Divine providence of G-d upon his creations, revealed his miraculous signs and wonders, brought justice to the wicked, and repaid good to those who love him [that is, love his attributes]. This is all evident in the smiting of Pharaoh and Egypt, and in the redemption of Yisrael.
Why specifically was this month chosen [for the Exodus to occur in]? The reason is because Egypt worshiped the lamb, which is the first of the astrological signs [Aries] in the celestial band, and this sign functions during the month of Nisan. Pharaoh relied on this sign in addition to his own power to bring him success. This explains his behavior, which appeared quite humbled after the plague of hail, where he exclaims "The L-rd is righteous, and I and my nation are sinners!" [Shmos 9.27], only to change markedly after the locusts, where he "expelled them [Moshe and Aaron from before him]" [Shmos 10.11], and culminating in his harsh words to Moshe after the plague of darkness - "You will see my face no more!" [Shmos [10.28]. The reason for all this is that as Nisan approached Pharaoh felt increasingly secure since the time of this astrological sign's ascendancy was approaching.
This then is the meaning of G-d's statement to Moshe: "This month should be for you the head of the months...", meaning to say "This month that Pharaoh was waiting for - it will be the first of your months, because through it the belief in astrological powers was shown to be false, and only "G-d - He is the L-rd - in the heavens above and the earth below, there is none other" [Devarim, 4.39] - and Yisrael is his treasure. Therefore this month was fitting to be made the first of the months.
Furthermore, this month's great stature is the reason that the tabernacle was erected on its first day, as is recounted in the Torah portion of 'Pikudei', and the princes offered their sacrifices, each on his day, at the time of the Altar's inauguration, as recounted in the portion of 'Naso'. The same will be true in the time to come [the messianic era], when the Temple will be rebuilt in Nisan, as is recounted in the last chapter of the Talmudic tractate Sofrim 21.2. It is also written there that one does not say supplications ('Tachanun') the entire month of Nisan, and neither does one fast - excepting the fast of the firstborn on the eve of Pesach - or say 'Tzidkascha Tzedek' in the Mincha of Shabbos or deliver a eulogy. The prayer of 'Tzadok Hadin' [a prayer recited at a funeral] is not said either.
From the words of our teacher the Beis Yosef it is evident that the prohibition over fasting is only for a communal fast. A personal fast, however, is allowed. This can be seen from his words "Fasting in not practiced over a communal commemoration." On the other hand, our teacher the Rema writes as follows: "The custom is not to fast at all, even on the anniversary of the death of one's father or mother."
A bridegroom on his wedding day may fast [as is the custom], as I write later in chapter 573. Fasting over a troubling dream is obviously permitted, and it is not necessary for one to fast again as compensation for the first being on day that it was prohibited to fast on, as is done for Shabbos and festivals days.
And do not ask: "What special quality do the days after Pesach have that they share these laws?", for the answer is that since since the majority of the month is holy, [the remainder is treated likewise] ('Magen Avraham', end of comment 3). Truthfully, this reason is not even necessary, because the entire month is holy for reasons that we have already explained.
If one fasted on a Shabbos in Nisan because of a troubling dream, and therefore was required to fast an additional compensatory fast due to his fasting on the Sabbath, he should fast the following day even though it be in Nisan ('Magen Avraham', comment 6). If however he is close to the tenth of the month he should push it off until that day since that day is already a 'fast of the righteous' for reasons explained in chapter 580. The same would apply to Rosh Chodesh itself [the first day of a month], since it is a day on which some fast (see chapter 580 as well).
One does not say 'Mizmor Lesodah' [Psalm 100] on Pesach eve or on Pesach because the 'Todah' sacrifice [which is the subject of the psalm] had in it 'Chametz' [leavened bread]. Similarly, in the daily recitation of the sacrifices in the section headed by "Eizehu" ("איזהו") one does not say "...as if I had brought a Todah..." for the same reason. In addition, one does not say "E-l Erech Apayim" or "Lamnatzeach" [Psalm 20]. Sefardic communities do not say these [ALL OF THESE?] the entire month. Regarding the communal Torah readings, the "Yehee Ratzon" prayer immediately following the readings on Monday and Thursday are also not recited.
'Hazkarah' [Prayers said on the anniversary of a death, often at the graveside, CORRECT?] is not performed during Nisan. It has already been mentioned that 'Tazok Hadin' is not said, and it therefore follows that 'Kadish' would not be recited either (previous source, comment 5). However, one may said a Psalm and recite Kadish afterward. In particular, the custom is to recite Psalm 29 and follow it with Kadish. When the body of a deceased Torah scholar is present it should be obvious that a eulogy is said, as there is no festival exception for a Torah scholar, and certainly no exception effected by the month of Nisan itself. In regard to this see what I have written in chapter 420.
There is a custom to increase feasting somewhat on the day following a festival, and this day is known as 'Isru Chag'. In addition the custom is not to fast on this day, since it has somewhat the status of a festival. Now the Isru Chag of Shavuous is certainly a festival, for that was a day on which sacrifices were offered [CORRECT?], though this status has also been adopted for the day following Peasach and Sukkos as well. The Talmud itself recirds in Sukkah (45.2) "Whoever celebrates Isur Chag through some increase in feasting - the Torah considers as if he built an altar and sacrificed upon it an offering, as the verse states [Psalms 118.27]: "Bind the sacrifice [Heb. 'Isru Chag...'] with ropes until [it is brought to] the corners of the altar." Rashi, in one of the two explanations he offers, mentions that this in reference to Isru Chag (see there). It appears to me that the explanation is as follows: That the rejoicing on a festival, when performed for the sake of Heaven, is primarily found in the offering of the festival Shelamin sacrifices. If in one's joy and attachment to the L-rd he rejoices on the following day as well, when he eats of the Shelamin sacrificed on the previous day, (for Shelamin are eaten for two days and one night), his additional exuberance is counted, besides the offering itself, as if he had even built the altar.
It is related in Gemara Pesachim (6.1): "One should ask and expound upon the laws of Pesach before Pesach's arrival for thirty days". Commentators question this by pointing out the end of Gemara Megillah, which relates that Moshe enacted that the Israelites study the laws of Pesach on Pesach and the laws of Sukkos on Sukkos, which clearly implies that the obligation is only on Pesach itself. There are many answers to this question, for example that a distinction may be made as to the order of precedence for answering two question submitted where one relates to Pesach and the other does not; other explanations are offered as well.
The truth is that the Yirushalmi itself explains the distinction, in the first chapter of Pesachim (end of law 1): "...This applies to a gathering place", that is, in a house of study (school), where the scholars gather, that is where study begins thirty days before. As for the individual, his study need only be on on Pesach ('Chok Yaakov'). Nowadays the custom is that the Rabbi [of the community] expounds upon these laws on the 'Great Shabbos' ['Shabbos Hagadol'] that immediately precedes Pesach, and [for Rosh Hashana, Yom Kippur and Sukkos] on the 'Shabbos of Repentance'. There are those who also take the opportunity to exhort the people in the moral lessons of these festivals, to increase the people's emotional attachment to Torah and fear of Heaven. However, in regard to personal practical questions of Pesach observance this [the thirty day period] is not necessary, as each asks only what he requires for his situation, or at the very least general information regarding Pesach, and each will learn according to his ability (See Magen Avraham, comment 1).
All of Jewish people have the custom to collect funds to buy the poor Pesach flour for Pesach (Heb. 'Moas Chitim'), or to give the funds to purchase it themselves. Anyone who dwells in a city for twelve months becomes obligated to participate in its charity campaign. Nowadays that the custom has become to expect participation after dwelling in a city thirty days, one must contribute accordingly after that time. Even a Torah scholar is required to contribute, as this is a charity collection, and not a municipal tax.
The above applies to one who comes to dwell in a city for a time - he is one who has the time period of twelve months or thirty days. However, if one has decided at the outset to permanently move to this city his obligations to contribute takes effect immediately. A poor person is eligible to receive funds after dwelling in the city for thirty days. One who has not yet dwelled therein for thirty days does not confer an obligation on the citizens to provide him with flour, though they are still obligated to provide him with Matza each day, as would be the law for any wayfarer, who is permitted to take funds from the communal charity fund if he is in need while passing through (as is explained in 'Yoreh Deah', chapter 256. If a poor person has come to settle in the city permanently he must be provided with Pesach flour immediately, After all, why should the the one who accepts the funds be treated differently than the one who is obligated to contribute funds? Once a person has decided to settle in a city he is a full-fledged resident.
Proclamations in the synagogue for a great need are permitted in the whole month of Nisan, but nor during the month of Tishrei, for the reason given in chapter 602. [THESE APPEAR TO BE NEGATIVE TYPES OF PROCLAMATIONS, LIKE BANS AND THE THREATENING OATH ADMINISTERED TO WITNESSES, SEE THERE]
We have a custom to read the portion of the princes offerings from the beginning of the month, reading each one on his day. On the thirteenth day the reading commences from "And this was the inauguration of the Altar" and ends at "This is how the Menorah was made", which is read on behalf of the tribe of Levi. On the eve of Pesach after noon the portion of "This month should be for you..." is read, along with all portions that speak of Pesach. After the afternoon prayer ('Mincha') one reads the order of the Pesach sacrifice. This can be found printed in many editions of the Siddur.
On Pesach eve one should pray at as early as possible since one must finish his meal before the tenth hour, which is four hours into the day. The Maharshal advised that each person should take a bit of Pesach flour and eat it before Pesach together with any dish or bread so that if there is any concern that his flour contains leavened ('Chametz') material it can be considered to be consumed at that point before Pesach. This is purely an extra legal stringency, since there is no presumption ['Chazakah'] of prohibited status in law without cause, and furthermore, mixing flour and flour [if Chametz flour is mixed with regular flour] is like mixing liquid and liquid: if there are sixty parts to one of permitted material the prohibited material is nullified, and if not it isn't (Magen Avraham in chapter 430). Truthfully though, one could argue that his concern is based on the fact that there are those that argue that flour mixed with flour is actually comparable to mixed dry materials, which 'reawaken' to a prohibited status [upon Pesach's arrival, because the prohibited dry material remains in its place in the mixture and does not dissolve] ('Chok Yaakov'). [HOW WOULD TAKING SOME FLOUR BEFORE PESACH IN ANY WAY PREVENT THIS?]. Finally, there is custom to make the kugel dish on 'Shabbos Hagadol' (the Shabbos before Pesach) from Pesach flour.