Siman 489, Se'if 7

Shulchan Aruch, siman 489, se'if 7
"If one forgot and did not recite the blessing the entire night, he should count during the day without a blessing."
(Shulchan Aruch)

(In passing: these simanim are printed under the heading "Laws of Pesach" and not "Laws of Sefiras HaOmer," even though the content deals with the counting. There is no special reason for this; it is simply the custom of the printers.)

The real novelty in the words "without a blessing"

What the Shulchan Aruch is forbidding: Counting during the day needs no special permission at all. A person may count whenever he wishes, and even several times. The novelty here is that he may not recite a berachah over this counting.
Counting by day is an obligation: The intent is not that he has the option of counting during the day. He is obligated to count in order to fulfill the mitzvah, only without a blessing.
Why this matters going forward: Counting during the day is also what saves the blessings of the coming days. Precisely because he counted by day, he will be able to continue counting with a blessing.

"He should count during the day, in accordance with the opinion of many poskim, and after the fact the daytime counting is valid as a counting."
(Mishnah Berurah, s.k. 33)

The phrase "after the fact": From the wording of the Mishnah Berurah it emerges that this is not a counting of the first order. It is not fully "kosher" in the complete sense; it simply counts toward the tally after the fact.
What is lost and what remains: He has lost the blessing of that day, but the counting itself is credited to him, and therefore he is not treated as someone who skipped a day.

The four fundamental disputes on which this halachah rests

Biblical or rabbinic: Is Sefiras HaOmer nowadays a Torah obligation or a rabbinic one?
Days and weeks: Must one count both the days and the weeks, or is one of them enough?
One single unit or separate days: Are all forty nine days one continuous unit, or is each and every day a mitzvah standing on its own?
The definition of "temimus": "Seven complete weeks shall there be." Does this mean that the count as a whole must be complete from beginning to end, or that each individual day must itself be complete, meaning that one counts immediately at nightfall?

(Each one of these questions is disputed among the poskim, and none of them is decided. As a result the various opinions combine with one another: on the one hand we are strict not to recite a blessing, and on the other hand we are lenient so as not to lose the continuation of the count.)

The definition of temimus in practice

One who counts late at night: Someone who counts at ten or eleven at night has already missed several hours from the beginning of the night, and this is not full temimus. Still, since most of the twenty four hour period (night and day) is still ahead of him, it is considered complete.
The proof from a loaf and a half: At seudah shelishis, when a person has no other option, he takes a loaf and a half, and according to many poskim that suffices in place of two whole loaves, since a half is treated as a whole. Certainly a whole loaf is better, but when there is no other way, this is enough. So too here: half of the day is treated as a full day.
Once morning has come: When the whole night has passed, twelve hours are already gone and only eight or nine remain before him, and that is not complete. This is why the Shulchan Aruch specified "forgot and did not recite the blessing the entire night": as long as it is still night, everything is in order.

Until when can one make up the count during the day

The time for making it up: Until sunset he can certainly make it up. Bein hashemashos is already problematic, since it is doubtful whether it is day or night.
Day forty nine: There is a practice of extending the time on the forty ninth day. Not everyone accepts it, and it will be explained in its place.

"Without a blessing, since one must take into account the opinion of the poskim that the time for counting is only at night, and it would be a blessing in vain. Nevertheless, from here onward he counts every night with a blessing, and he is not like one who skipped an entire day and did not count in it at all."
(Mishnah Berurah, s.k. 34)

Why no blessing during the day: According to some poskim the time for counting is only at night, and therefore a blessing recited during the day is liable to be in vain.
The root of the derivations: The omer itself was counted during the day, but its harvesting began at night, and the matter depends on the derivations from the verses. That is the source of the differing opinions.
Circumstances beyond his control make no difference: In principle there is no distinction between one who forgot and one who was prevented; in both cases the ruling is the same.
The combination that allows him to continue: On the one hand we rely on the poskim who hold that temimus means from beginning to end, and that the gaps in the middle need not be complete; therefore he may count even late in the day. On the other hand we rely on the opinions that each day is an independent unit; therefore losing the blessing of this day does not affect the following day.
This is not a case of "doubtful blessings": Although there is a rule that in a doubt about a blessing we are lenient and do not recite it, here the doubt is not about the blessing but about whether the counting was done properly. If the counting is in order, he is permitted to recite the blessing.

Siman 489, se'if 8: one who skipped a day, and one who is in doubt

"If one forgot to recite the blessing on one of the days, whether the first day or any of the others, he counts the remaining days without a blessing. But if he is in doubt whether he skipped one day and did not count, he counts the remaining days with a blessing."
(Shulchan Aruch)

"Forgot to recite the blessing: meaning that he did not count, and did not remember until the next counting... And the same applies if he discovered that yesterday he erred in the number; his status is that of one who did not count at all."
(Mishnah Berurah)

What "forgot to recite the blessing" means: If he counted but did not recite the blessing, everything is fine, since the blessing is not a prerequisite for the mitzvah. Therefore the Mishnah Berurah explains that the Shulchan Aruch is speaking of one who also did not count at all.
The case: He did not count the fifth day, and did not remember until the sixth day. In such a case he has lost the blessings for the rest of the count.
Erred in the number: One who discovers that yesterday he erred and said a different number has the status of one who did not count at all.
In doubt whether he skipped: If he does not know clearly that he skipped a day, he counts the remaining days with a blessing.

In passing · One who knows in advance that he will be unable to count partway through

The case: A person is told before Pesach that during the days of the sefirah he will undergo surgery and will be incapacitated for a day or two, and will certainly be unable to count on that day. Does he begin counting with a blessing from the start of the sefirah, or are these blessings in vain, since he knows from the outset that he will not complete the count?
The difference from one who forgets: With one who forgets, something happened after the fact, and until then he recited the blessings properly. Here he knows from the very beginning that he will break off in the middle.
It depends on the question of the single unit: If each day is a mitzvah in its own right, there is no concern here; if the whole sefirah is one continuous unit, the question stands. And the proof that there is something to this is that one who missed reciting the blessing for a single day does not continue to recite it.

The proof from the words of the Ritva and the Rashba regarding washing the hands

The case: A person washed his hands for a meal and recited the blessing of al netilas yadayim, and when he came to recite Hamotzi it turned out that the bread had disappeared (the cat had eaten it), and all he had left was cake, which does not require washing.
The question: Did he utter Hashem's Name in vain, since in the end he did not eat bread and was not obligated to wash, or was he acting properly at the moment he washed his hands?
The Rashba's answer: One cannot say that he recited a blessing in vain. The man did what was required of him, and what happened afterward through no fault of his own does not turn his blessing into one recited in vain.

(This is a broad discussion, and the Rishonim bring more complicated examples of blessings of this type.)

The practical implication

The view of a large number of poskim: He should recite the blessing and count. Right now he is obligated to count, and especially according to the Rashba's approach, that he is doing what is required of him at the moment he acts.
The future is not in our hands: There is no certainty that the surgery will take place. It may be postponed, there may be a doctors' strike, and it may turn out on further examination that he does not need it at all. We rely on Heaven's kindness.
After the surgery: He has lost the blessings for the remaining days, and even though he is not at fault in the slightest, there is nothing to be done and no way to repair it.

In passing · The parameters of oness and of fault

Is forgetting considered oness: It is worth examining whether one who forgets is considered to have been prevented by circumstances or whether he is at fault for forgetting, and likewise one who fell asleep, who arguably should have been careful not to doze off. The matter is borderline, and by and large we look at it as a form of oness. As far as the halachah goes it makes no difference: a mishap occurred and he lost a day through no fault of his own.
The example from tefillin: A man wore tefillin that he received from his father, and years later they were checked and found to be invalid. Seemingly he did his part and is not at fault, yet in practice he did not wear tefillin for all those years. This is a delicate question that the masters of mussar discuss, and it cannot be resolved simply.
The example of one who stumbles: A man walking down the street who trips on a stone and breaks his arm is not at fault at all, and the same is true even if someone threw a stone at him from a window. Nevertheless, in practice he has no use of his arm for a month. Being blameless does not change the actual situation.

In passing · A bar mitzvah boy and a convert in the middle of the sefirah

One who becomes bar mitzvah during the sefirah: He becomes bar mitzvah on the tenth day, and before that he was not obligated. May he begin counting with a blessing?
One who converts during the sefirah: The very same question, regarding a convert who becomes a Jew in the middle of the days and is obligated in the counting from now on.
The root of the dispute: Everything depends on the question of whether the sefirah is one single unit, in which case he has lost the days that preceded, or whether each day stands on its own. There is a broad dispute about this.

In passing · A rav who forgot to count, and human dignity

The case: In shuls where the rav is the one who counts the sefirah publicly every day, and on one occasion he forgot. If he no longer counts, the whole congregation will find out.
The view of some of the tzaddikim: He should not count, so that he will feel shame, and through that he will be more careful and grow stronger; the matter will eat at him from within and bring him to improve.
The view of others: One may not shame a person publicly, all the more so a rav who lectures to and rebukes the congregation; therefore some poskim hold that he may count with a blessing.
What this relies on: On the opinions that each day is a mitzvah in its own right, on the opinions that the counting nowadays is rabbinic, and on the principle in the Gemara that human dignity overrides a negative commandment. And since this is no more than a possible blessing in vain, we combine the lenient factors.

In passing · Fulfilling another's obligation in the blessing of the sefirah through arvus

The suggested solution: The rav turns to one of the congregants and asks him not to recite the blessing himself that night, but rather to listen to the rav's blessing recited aloud, with the rav intending to fulfill his obligation for him. That way the congregation knows nothing. Prominent rabbanim conducted themselves this way.
Blessings over pleasure: A person cannot fulfill another's obligation unless he himself is eating. One who is not eating an apple cannot recite the blessing on behalf of the one who is.
Blessings over mitzvos: Here one can fulfill another's obligation through arvus, since all Jews are responsible for one another. That is why a person blowing shofar for a fourth minyan, even though he has already fulfilled his own obligation, recites the blessing on behalf of those who have not yet had it recited for them.
Sefiras HaOmer: The text of the blessing is "Who sanctified us with His commandments and commanded us," so it is a blessing over a mitzvah, and seemingly one person can fulfill another's obligation with it.

(The discussion remains open for the next shiur, as does the distinction between the blessing of the sefirah and other blessings over mitzvos.)