Siman 489, Se'if 2

Shulchan Aruch Siman 489: Completing the Mishnah Berurah on Se'if 1

"There is a custom to say after the counting, 'May it be Your will that the Beis HaMikdash be rebuilt, etc.'... and some are accustomed to say also the mizmor 'Elokim yechaneinu.'"
(Mishnah Berurah, s.k. 10)

(Here the Mishnah Berurah is not explaining the words of the Shulchan Aruch; rather, he is adding two things that people were accustomed to say after the counting.)

The texts said after the counting

Yehi Ratzon, that the Beis HaMikdash be rebuilt: An early text, mentioned already in the Tosafos and in the Rishonim, and some trace its beginnings back to the era of the Geonim. Saying it is meant to make the counting serve as a remembrance of the Mikdash and of the mitzvah of the omer.
The mizmor Elokim yechaneinu: A chapter of Tehillim, whose recitation at this point apparently entered through Kabbalah, though it is possible that there was such a custom even earlier.
Further additions from Kabbalah: Following the mizmor, "Ana B'Koach," "Ribono Shel Olam" and "L'sheim Yichud" also entered the text. None of these are mentioned here by the Mishnah Berurah at all.
The order of recitation: The order was set according to how early the sources are: first "Yehi Ratzon," which is the earliest and best established (and some trace such early texts to the Rokeach and to Rabbi Yehudah HaChassid), and after it the mizmor and the rest of the additions.

Saying the additions and the text of "L'sheim Yichud"

The view of those who object: Some wrote that these additions should not be said at all, since they are matters of Kabbalah and hidden secrets that are not given over to every person.
The power of the printers: Since these texts were printed in nearly every siddur, the custom of saying them spread among the Jewish people, and because of that even the poskim entered into discussing them.
The discussion about the wording "mitzvas asei": In the phrase "to fulfill the positive commandment (mitzvas asei) of Sefiras HaOmer," some object to the word "asei," because the matter depends on the dispute whether Sefiras HaOmer nowadays is min haTorah or rabbinic; in their view one should say "to fulfill the mitzvah of Sefiras HaOmer." Others say that even if the mitzvah is rabbinic, it can still be called a rabbinic positive commandment, and there is no difficulty in that.
In practice: Saying these texts depends on the custom of one's community and on what a person takes upon himself, and one who does not say them has lost nothing in his fulfillment of the mitzvah.

The Mizmor of the Menorah

The opening of the mizmor: The mizmor does not begin with the words "Elokim yechaneinu" but with "Lamnatzeiach binginos mizmor shir," and only afterward "Elokim yechaneinu vivarcheinu." The Mishnah Berurah used the identifiable phrase from the body of the mizmor so that it not be confused with others, and he does not elaborate on reasons.
The shape of a menorah: The mizmor is printed in the shape of a menorah, mainly in Sephardic siddurim, and from this comes its name, "the Mizmor of the Menorah."
The seven branches: When you remove the opening verse, seven verses remain, corresponding to the seven branches of the menorah, and the heading of the mizmor is written above.
The count of forty nine: In the body of the mizmor, after removing the first verse, there are forty nine words, and in the central verse, which is like the middle branch of the menorah, there are forty nine letters (and this depends on full and defective spellings).
The connection to Sefiras HaOmer: The mizmor has no special connection to Sefiras HaOmer; its significance stands on its own in the number forty nine. Since the counting is forty nine days, it came to be used for this purpose as well.
A word for each day: Some siddurim go further and attach to each day of the counting the corresponding word from the mizmor.

Mishnah Berurah s.k. 11: changing the wording of the counting

What the Acharonim wrote: One who on the thirty ninth day said "forty minus one" instead of "thirty nine": it was already explained above that according to the Mishnah Berurah he has fulfilled his obligation, even though the matter is not simple.
The question that remains: Is this allowed specifically with the wording "forty minus one," which is a number mentioned in the words of Chazal, or with any number in the form of "minus one," and even in the form of "minus two"?

Se'if 2: They erred on a cloudy day

"If they erred on a cloudy day and recited the blessing on Sefiras HaOmer, they count again when it becomes dark. And those who are meticulous do not count until the stars come out, and so it is proper to do."
(Shulchan Aruch, Siman 489, se'if 2)

The source of the ruling: a responsum of the Rashba

The source: The Mishnah Berurah in s.k. 12 notes that this ruling comes from the Rashba in a responsum, siman 154.
The incident: On a cloudy day the congregation thought the sun had already set, davened Maariv and counted Sefiras HaOmer, and after they dispersed it became clear that the sun was still shining. In their times there were no clocks or printed zmanim charts, and the estimate was made by the appearance of the sky.

(There are roughly eight volumes of responsa of the Rashba, and here it is not stated from which volume. When no volume is cited, the reference is generally to the first, which is the largest of them and contains more than fifteen hundred responsa.)

The distinction between Maariv and Sefiras HaOmer

Regarding Maariv: They need not daven again, because of tircha d'tzibura, the burden on the congregation.
Why davening Maariv early is permitted to begin with: Fundamentally, it was permitted to daven Maariv right after Minchah because if the congregation would wait until the proper time, people would scatter to their homes and not come back, and tefillah b'tzibur, whose importance is great, would be lost. And since on an ordinary day they daven early in just this way, what happened here is no worse than that.
Regarding the counting: The reason of tircha d'tzibura does not help, since the counting itself contains an error in the number:

"How can he say 'ten days' when it is only nine, for that day was the ninth and not the tenth until the stars came out."
(Mishnah Berurah, s.k. 12)

Mishnah Berurah s.k. 13: he counts again with a blessing

The ruling: He counts again with a blessing as the halachah requires, since nothing at all was accomplished by what he counted earlier: he said "today is ten days" when it was only nine, so it turns out he erred in the count and did not count at all.
No comparison to tosefes Shabbos: One cannot argue that just as there is tosefes Shabbos, adding on to Shabbos, so too the counting should work after the fact or partially. This distinction needs explanation, and here is its definition:
- A halachic day: With tosefes Shabbos a person accepts upon himself a weekday period as far as the laws of Shabbos are concerned, and he may light candles, make Kiddush and daven the Shabbos tefillah. Halachically it is already Shabbos.
- A factual day: As far as the workings of creation go, it is still Friday, and a person has no power to turn the sixth day into the seventh.
- And regarding Sefiras HaOmer: The counting must take place on the actual day, from the requirement of "temimos," complete days, meaning on the true day, and therefore one cannot count early and call the ninth day the tenth.

Mishnah Berurah s.k. 14: "and those who are meticulous"

"That is to say, strictly by law it would have been possible to be lenient and count from when it grows dark, even before the stars come out, since bein hashemashos is a doubt as to whether it is night, and in a rabbinic doubt we rule leniently, for the counting nowadays is rabbinic according to most poskim. Nevertheless, it is not proper to enter into a doubt at the outset, and therefore those who are meticulous wait for the stars to come out, which is certainly night."
(Mishnah Berurah, s.k. 14)

The side of leniency: Bein hashemashos, twilight, was defined by Chazal as a doubt whether it is day or night. If it may be night, then the new day has already begun and one may count during it. And since Sefiras HaOmer nowadays is rabbinic according to most poskim, a rabbinic doubt is ruled leniently.
The difficulty in fixing the precise time: A person cannot know the exact moment the stars come out, whether it is with one star or two or three, and whether they are close together or far apart, so relying on bein hashemashos is shaky.
The practical conclusion: As long as a person has a simple and clear solution available, he should not enter into a doubt at the outset, and therefore one waits until it is definitely night. Someone who runs into difficulty and cannot wait has what to rely on during bein hashemashos, but this is not the standard practice.

Mishnah Berurah s.k. 15: "and so it is proper to do"

"That is to say, at the outset. Nevertheless, after the fact, if he recited the blessing during bein hashemashos, he has fulfilled his obligation... And there is one who questions this and holds that it is proper for him to count again at the emergence of the stars without a blessing."
(Mishnah Berurah, s.k. 15)

L'chatchilah and b'dieved: The phrase "and so it is proper to do" was said with regard to the preferred practice; after the fact, one who recited the blessing and counted during bein hashemashos has fulfilled his obligation.
The view that he should count again without a blessing: Since the counting itself involves no prohibition at all, and a person can recite the number several times a day without transgressing anything, it is worthwhile to count again after the stars come out in order to remove himself from the doubt.
And why without a blessing: The entire problem is the blessing. Since it is possible that he already fulfilled his obligation with the counting during bein hashemashos, repeating the blessing could be a berachah levatalah, a blessing in vain, and therefore he only counts again.
To whom this is addressed: These words were said to one who is prepared to wait and be meticulous. As for someone who has no patience and davens Maariv during bein hashemashos, to him it is proper to say that he should count a second time at night, since better safe than sorry.

Se'if 3: One who counts with the congregation while it is still day

"One who davens with the congregation while it is still day counts along with them without a blessing, and if he remembers at night he recites the blessing and counts. And even if he separated from the congregation and had already intended to fulfill his obligation, he counts again with a blessing at night."
(Shulchan Aruch, Siman 489, se'if 3)

The case: A person davening in a shul where Maariv is davened immediately after Minchah, even before bein hashemashos, and in that minyan they count the omer. He wants to daven with a congregation, whose importance is great, and not to daven alone at home.
The ruling: He counts along with them without a blessing, and when night arrives he recites the blessing and counts. The discussion of the reason for this ruling, and of the matter of making a condition in mitzvos, will be explained next time.

Why should he count with them at all

So as not to separate from the congregation: One who stands in the midst of the congregation and does not count with them appears to be separating himself from them.
So that he not forget: One who counts with the congregation at that time is reminded of the counting and will not come to forget it.
The virtue of counting with a congregation: Some learned from here that there is value in counting the omer together with a congregation. And so many poskim ruled regarding one who walks into shul just as the congregation has finished Maariv and is counting the omer, that he should count with them and not begin his own tefillah.
A remembrance of the harvesting of the omer: In the times of Chazal they did not count the omer in a public gathering, but the harvesting of the omer, which is the beginning of the whole matter, was done publicly and with great fanfare because of the Tzedukim, and therefore there is significance to a public remembrance in this matter.
Other things that have a special value in public: The poskim wrote this way about other matters as well, such as one who enters a shul to learn or to daven while the congregation is saying Aleinu L'Shabeiach or the Thirteen Attributes of Mercy, that he should say it along with them.
B'rov am hadras Melech: By joining them he enlarges the congregation, so that if there were fifteen there are now sixteen, and he himself also gains the virtue of saying it in a group.

In passing · Questions asked during the shiur

1. Why Krias Shema is not mentioned in the incident of the cloudy day

A precise reading of the Rashba: The Rashba answered that they need not daven again, and he said nothing about Krias Shema.
The distinction: Maariv and Krias Shema are two separate matters. One may daven Maariv early, and each person will read Krias Shema at its proper time at home.
Why they did not ask about it: That congregation was accustomed to daven Maariv early, and knew the halachah that one must read Krias Shema again afterward. Their question was only about the counting.

2. The measures of the zmanim and the definition of bein hashemashos

The discussion in the Biur Halachah: The Biur Halachah enters into the question of how much earlier than the emergence of the stars one may be lenient, and what the length of bein hashemashos is. These matters depend on the sugyos of the measures of the zmanim and were not explained here.
Other places where the question recurs: These questions come up every day and in all sorts of matters, among them the Ne'ilah tefillah on Yom Kippur and until when the Kohanim may go up to duchan.