סימן קכ סעיף א
בְּלֵיל שֵׁנִי שֶׁל פֶּסַח, מַתְחִילִין לִסְפֹּר סְפִירַת הָעֹמֶר. וְסוֹפְרִין מְעֻמָּד. הַמִּצְוָה הוּא לִסְפּוֹר תֵּכֶף בְּהַתְחָלַת הַלַּיְלָה, אַחַר צֵאת הַכּוֹכָבִים. וּבְדִיעֲבַד, זְמַנָּהּ כָּל הַלָיְלָה. בְּבֵית הַכְּנֶסֶת בְּלֵילֵי שַׁבָּת וְיוֹם טוֹב סוֹפְרִין לְאַחַר הַקִּדּוּשׁ, כְּדֵי לְהַקְדִּים קְדֻשַּׁת הַיּוֹם. וּבְמוֹצָאֵי שַׁבָּת וְיוֹם טוֹב, סוֹפְרִין קֹדֶם הַבְדָּלָה כְּדֵי לְאַחֵר יְצִיאַת הַיּוֹם. וּכְשֶׁחַל יוֹם טוֹב הָאַחֲרוֹן בְּמוֹצָאֵי שַׁבָּת, שֶׁאוֹמְרִים קִדּוּשׁ וְהַבְדָּלָה עַל כּוֹס אֶחָד, סוֹפְרִין גַּם כֵּן קֹדֶם כְּדֵי לְאַחֵר אֶת הַהַבְדָּלָה.
On the second night of Pesach, we begin counting the Omer.1Since this is a mitzvah, that is done only at a certain, specific time, women are exempt from counting the Omer. Magein Avraham says that women have since accepted this mitzvah as an obligation, but Mishnah Berurah says that in our areas, women are not accustomed to count the Omer. He quotes from Shulchan Shlomo that women certainly should not say the berachah. (Mishnah Berurah 489:3) You should stand during the counting.2You should also stand for the berachah. If, however, you did count while sitting, you have still fulfilled your obligation (and you need not count over again). (Ibid. 489:6) The mitzvah requires that the Omer be counted, as soon as possible after nightfall,3Counting the Omer is done after the Maariv prayer, before saying Aleinu. Later Poskim rule, however, once the stars have appeared, the Omer may be counted even before Maariv. (Ibid. 489:2,18) after (three medium-size star) stars begin to appear. If you did not count at the beginning of the evening, you may count the entire night. In the synagogue, on the eve of Shabbos and Yom Tov, we count after the Kiddush is said, in order to give precedence to the (proclamation of the) holiness of the day.4At home, however, we must count the Omer before Kiddush, as it is forbidden to eat before counting the Omer. (Ibid. 489:39) At the conclusion of Shabbos and Yom Tov, we count before the Havdalah is said, in order to delay the end of the day. If the last day of Yom Tov occurs on Shabbos night, when the Kiddush and the Havdalah are said over one [the same] cup of wine, we also count before, in order to postpone the Havdalah.
תנא דבי אליהו כל השונה הלכות בכל יום מובטח לו שהוא בן העולם הבא שנאמר הליכות עולם לו אל תקרי הליכות אלא הלכות (נדה ע"ג.)