The Mitzvoh
1. There is a mitzvoh to count the omer from the second night of Pesach for 49 days; the 50th day is Shavuos. Some hold that even nowadays this mitzvoh is deoraiso (רמב"ם, חינוך מצוה ש"ו ועוד ). Others hold that nowadays it is merely a derabonon enactment to remember the Beis Hamikdosh, where they brought the korban omer (מנ"ח בדעת החינוך, טור ושו"ע ). This may be the reason we say the 'horachamon' immediately after counting the omer (שעה"צ סי' תפ"ט סקט"ו ).
Is Each Day its Own Mitzvoh?
2. Some rishonim hold counting each day is a mitzvoh independent of the other days. Therefore, if one forgot to count a day, he may continue to count the rest of the days with a brochoh (תוס' מנחות דף ס"ו ע"א ד"ה זכר למקדש, רא"ש מאירי סוף פסחים, ריטב"א מגילה ועוד ).
3. Others hold that since the posuk says 'temimos' [whole], all of the days of sefiroh are parts of one big mitzvoh. Therefore, if one missed a full day, he does not fulfill a mitzvoh by continuing to count (שי' הבה"ג הובא בתוס' מגילה דך כ' ע"ב ובמנחות שם ). See 16, below.
Standing
4. Sefiras ho'omer must be done standing (שו"ע סי' תפ"ט ס"א ). The brochoh must also be said standing (מ"ב סק"ו ). Therefore, during the sefiroh one should not lean heavily on any object (מ"ב סי' תקפ"ה סק"ב ).
5. Bedieved, if one counted sefiroh while sitting - and certainly while leaning – he is yotzei. Similar to the halochoh regarding tefilloh, a sick or elderly person may count sitting (מ "ב סי' צ"ד סק"כ ).
Onein
6. If someone's relative passed away, lo oleinu, during sefiroh at night and was not yet buried, he is exempt from all mitzvos and should not count sefiroh. However, he should count the next day after the burial without a brochoh and continue to count for the rest of the days with a brochoh.
7. If he will be an onein all night and all day, he should count at night without a brochoh to enable himself to continue counting with a brochoh and not lose 'temimos' (שו"ת נודב"י מהדו"ק א ו"ח סי' כ"ז, ביאה"ל סי' תפ"ט ס"ח ד"ה בלא ברכה ).
The Time to Count
Counting at Night
8. On the first night of sefiroh, one should count as close as possible to the beginning of the night in order to fulfill 'temimos' (מ"ב סי' תפ"ט סק"ב ). According to the opinion that each day is a separate mitzvoh, one should count every night as close as possible to the beginning of the night (חיי אדם כלל קל"א ס"ב, ביאה"ל ס"ח ד"ה סופר ).
9. Even so, as long as it is before alos, one can make a brochoh (שו"ע הרב ס"ג ) and fulfills 'temimos' somewhat (מ"ב סק"ד ).
10. Although one should count at the beginning of the night, he should only count after Maariv (שו"ע ס"א ), which is todir (חק יעקב סקט"ז ). Sefiroh should precede Oleinu to make it as close as possible to the beginning of the night (מ"ב שם ). Some count after Oleinu (מעשה רב סוף הל' תפלה אות ס"ט, מנהג כמה חסידיות ועוד ) to avoid interrupting the structure of davening (כף החיים ס"ק קב ).
11. A set minyan for Maariv. Someone who consistently davens at a Maariv later in the night should continue to do so and count sefiroh afterward rather than counting alone at the beginning of the night. He may also eat before Maariv since he davens in a fixed minyan (אג"מ או"ח ח"ד סי' צ"ט ).
Bein Hashmoshos
12. One should ideally count only from tzeis and on (שו"ע סי' תפ"ט ס"ב ). However, a chinuch-age child may count at bein hashmoshos [after shkiyoh] with a brochoh, especially in areas of the world where tzeis is late (כ"ק מרן גאב"ד ירושלים ). The same is true for elderly people who go to sleep early (מו"ר בעל שבט הקהתי אורח כהלכה סי' י"ד אות ב').
13. Before Rabbeinu Tam. Even one who is normally strict on Motzei Shabbos and Yom Tov and does not do melochoh deoraiso before Rabbeinu Tam should count sefiroh with a minyan before Rabbeinu Tam rather than alone after Rabbeinu Tam, since most poskim hold that sefiroh nowadays is only derabonon (שו"ת מנח"י ח"ט סי' נ"ו ).
Sefiroh by Day
14. If one forgot to count at night, he may count by day without a brochoh (שו"ע ס"ז ). He may continue to count the remaining nights with a brochoh (תרומת הדשן סי' ל"ז, מ"ב סקל"ד ).
15. Therefore, it is worthwhile for one to accustom himself to count every day [after Shacharis, for example], so that if he forgets to count one night, he may continue with a brochoh for the remaining nights (כף החיים סק"פ ).
Mistakes in Counting
Skipped a Day
16. Since there is a machlokes whether each day is a separate mitzvoh or part of one mitzvoh (above, 2, 3), the Shulchan Oruch rules that if one forgot to count an entire day, he should count the remaining days [because of the opinion that each day is separate] without a brochoh [due to the opinion that it is one mitzvoh] (שו"ע סי' תפט ס"ח ). He should listen to someone else make the brochoh and answer amein with intent to be yotzei before counting (מ"ב סקל"ז ).
17. Unsure if he forgot. If one is not sure if he missed a day, he may continue for the remainder of sefiroh to count with a brochoh (שו"ע שם ) because it is a double sofeik (מ"ב סקל"ח ) and most poskim hold that each day is a separate mitzvoh (שעה"צ סקמ"ו ).
18. Remembered at bein hashmoshos. If one remembered at bein hashmoshos that he did not count that day, he may count without a brochoh and count the rest of sefiroh with a brochoh because of the double sofeik (שו"ת בית שלמה ח"א סקק"ב, שו"ת מנח"י ח"ט סי' נ"ז ). Also, one who follows zman Rabbeinu Tam even for derabonons may count until Rabbeinu Tam shkiyoh and continue afterward with a brochoh (שו"ת מנח"י שם ).
19. Shliach tzibbur who forgot. A shliach tzibbur who previously forgot a complete day and is now counting without a brochoh may, according to most, ask someone in the minyan who is still counting with a brochoh not to make a brochoh and be yotzei with his [the shliach tzibbur's] brochoh. This works based on the concept of 'arvus' (מאמ"ר סק"י, מדרש פנחס דף ל"א ע"ב, הגרי"ד מבריסק הובא בשו"ת הר צבי ח"ב סי' ע"ה ).
20. However, some say that since he cannot make the brochoh for himself, he may not be motzi someone else (כף החיים סקצ"א ). That said, if the fixed shliach tzibbur forgot and would be embarrassed, he may certainly be meikel (שו"ת דברי משה ח"א סי' ל').
21. Rav who forgot. If a rav generally counts out loud publicly with a brochoh, but forgot one day and it will be degrading and disrespectful to the kovod haTorah for him not to make a brochoh, he may continue to count with a brochoh even without the above method [if it will be degrading even in front of the gabbai], and rely on the rishonim that hold each day is a separate mitzvoh (שו"ת שבט הלוי ח"ג סי' צ"ו וח"ד סי' קנ"ז בהערה לסי' צ"ו ).
Knowing the Number During the Brochoh
22. Ideally, one should be aware which day he is about to count before saying the brochoh (מ"ב סי' תפ"ט סקכ"ט ) to avoid an interruption after the brochoh. If a person did interrupt, even longer than kedei dibbur, but did not get distracted, he does not need to make a new brochoh (מ"ב סי' ר"ו סקי"ב ).
23. If, during the brochoh, one thought it was Day 4 for example, but realized immediately afterward that it is Day 5 and counted 5, he is yotzei (שו"ע סי' תפ"ט ס"ו ).
24. If, during the brochoh, he thought it was 4, and he counted 4, but realized within kedei dibbur of his last word (מ"ב סי' תפ"ז סק"ד ) that it was 5 and corrected himself, he is yotzei (מ"ב סי' תפ"ט סקל"ב ). When correcting himself, he does not need to repeat "Today is..."; after he mistakenly said "four days of the omer," it is enough to simply say "five days of the omer" (מ"ב שם ).
Counting Days and Weeks
25. The Torah says to count 50 days, and to count seven weeks. From this, we learn that one must count days and weeks (שו"ע ס"א ובמ"ב ). However, the main application of counting the weeks is at the end of each full week. When we say on Day 8, for example, "...which is one week and one day," that is just a minhag (שעה"צ סקכ"ח ).
26. Only counted days at the end of a week. If, say, on Day 7, one said "Today is seven days of the omer" without mentioning that it is one week, some say he is yotzei bedieved (מג"א וחק יעקב ); others say he must count again properly with a brochoh (פר"ח א"ר ). Practically, he should count again without a brochoh (מ"ב סק"ז ). If he forgot to count again, he may count the remaining nights with a brochoh (מ"ב שם ).
27. Forgot the weeks on the other days. If, say, on Day 8, one just said "Today is eight days" without mentioning weeks, he is yotzei (מ"ב סק"ט ).
28. Only counted weeks at the end of a week. If, say, on Day 14, one simply said, "Today is two weeks of the omer," all agree that he was not yotzei (מ"ב סק"ז ) and must recount with a brochoh.
29. Only counted weeks on the other days. If one did not mention the total number of days on a day other than the end of a week, e.g., on Day 16 he said, "Today is two weeks and two days of the omer" without saying the number sixteen, he is yotzei (מג"א, ש ע ה"צ סקי"א ), since by adding "and two days," bedieved he also counted the days.
30. Contradiction. If, say, on Day 16, one said, "Sixteen days, which are two weeks and three [instead of two] days of the omer," he is yotzei (שו"ת שו"מ מהוד"ד ח"ג סי' קכ"ז, שו"ת שרגא המאיר ח"ד סי' ס"ב ).
31. However, if this happened at the completion of a week, e.g., on Day 14 he said, "Today is fifteen days, which are two weeks of the omer," he is not yotzei, since he didn't count the days, and he must recount with a brochoh (see above, 28).
Abbreviations
32. If one counted with an abbreviation, e.g., "Today is 'hei' days of the omer" instead of "five days," or "yud gimmel" instead of "thirteen," some poskim say he is yotzei (כנה"ג בשם מהר"ש הלוי ); others say he is not (פר"ח הובא בשע"ת סק"ו ). Thus, if one counted with an abbreviation, he should recount without a brochoh (ביאה"ל ס"א ד"ה מונה והולך ).
Counting with the Middoh
33. Each day has a unique middoh. Day 20, for example, is 'yesod shebetiferes.' If, before counting, one mentioned that day's middoh, it is not considered as if he counted, and he may count with a brochoh (מפי בעל שבט הקהתי ).
Unintentionally Counted
Mitzvos Require Kavonoh
34. The poskim debate whether or not mitzvos need kavonoh. According to the opinion that they do not, if one said the text of sefiroh, even without kavonoh to be yotzei, he is yotzei and may not make a brochoh. According to the opinion that mitzvos need kavonoh, if one counted without kavonoh to be yotzei, he may recount with kavonoh and a brochoh.
35. We pasken that mitzvos require kavonoh (או"ח סי' ס' ס"ד ). Therefore, if one unintentionally counted sefiroh, he must certainly recount with kavonoh to be yotzei. However, we take into account the opinion that mitzvos do not need kavonoh, so he should not make a brochoh on the second counting, especially if sefiras ho'omer is derabonon nowadays, as most poskim hold (מ"ב סקי"ז ).
When Asked What Day It Is
36. If one asks his friend which day of the omer it is, he should not say, "Today is five days" if he has not counted yet. If he does, he may no longer count that day with a brochoh according to the opinion that holds mitzvos do not need kavonoh. He should say, "Yesterday was four" (שו"ע ס"ד ).
37. One must be careful about this from shkiyoh and on (שו"ע שם ). Some say he should ideally be careful from plag. Bedieved, if he said this after plag, he may still make a brochoh (שו"ע הרב סט"ו ). There is no need to be careful about this before plag.
Did Not Say "Today Is..."
38. If he did not begin his response with "Today is," but merely responded, "23 days of the omer" for example, he may still count with a brochoh, since without saying "Today is...", one did not count properly (מ"ב סק"כ ). However, one should ideally always answer with the prior day’s count (כף החיים סקנ"ג ).
Did Not Say "Bo'omer/Lo'omer"
39. If one responded by saying, "Today is 23 days," without saying, "of the omer," he may not count with a brochoh (מ"ב סקכ"א ), since bedieved one is yotzei without saying "of the omer" (מ"ב סק"ח ).
In Question Form
40. If one asked, "Is today such-and-such days?" he may still count with a brochoh, because asking a question is not considered counting (הגר"ש וואזנר, קובץ מבית לוי עניני ניסן עמ' פ"ד אות ז').
Mentioned Lag Bo'omer Without Kavonoh
41. One should be careful from bein hashmoshos of Erev Lag Bo'omer not to say, "Today is Lag Bo'omer," since that would cause him to miss counting with a brochoh that night, as there are those that hold one is yotzei sefiroh with an abbreviation (above, 32).
42. If, on Lag Bo'omer night, one said, "I can listen to music because it is Lag Bo'omer today," he may still count with a brochoh afterward, since he was referring to the day called "Lag Bo'omer;" not to the day's count (כף החיים סק"ל, שו"ת אור לציון ח"ג פט"ז תשובה ד').
Didn't Mention the Weeks
43. Some say that one only must be careful not to say what day it is for the first six days, before the weeks become part of the count, but from Day 7 and on, if one said "such-and-such days" without mentioning the weeks, he may still count with a brochoh (פר"ח וא"ר ). One may rely on this since this is only an issue according to the opinion that mitzvos do not need kavonoh (above, 34), and he may therefore make a brochoh on the sefiroh (שעה"צ סקכ"ח ).
