Because of the exalted themes behind the moon’s renewal, the person who recites the Blessing of the Moon is considered as one who receives God’s Presence (the Shechinah). Thus, Tanna D’vei Rebbi Yishmael states, “Had the Jews been privileged to greet their Father in Heaven only once a month (when reciting Birkat HaLevanah), it would be sufficient” (Sanhedrin 42a). Therefore, Abaye concluded that one must honor the blessing and recite it while standing (ibid.). One who finds it difficult to stand should lean on his cane, or on a friend, and recite the blessing. If leaning is too difficult, he may say it while sitting.
The custom is to honor the blessing by saying it with a minyan. In the absence of a minyan, it is best to say it in a group of three, but according to the letter of the law one, may recite it alone. If one is concerned that waiting for a day on which a minyan can be gathered will cause him to forget to say the blessing altogether, it is preferable not to wait, and to say it alone (Biur Halachah 426:2, s.v. ella).
It is customary to leave the synagogue or one’s house and recite the blessing under the open sky. We learned above that Birkat HaLevanah is compared to greeting the Shechinah. Therefore, just as one goes out to greet a king, one should go out to recite this blessing. A person who is sick, or fearful that he might catch a cold if he ventures outside, may glance at the moon through a window and say the blessing indoors (Mishna Berura 426:21).
In order to honor the blessing, which contains an aspect of greeting the Shechinah, we are accustomed to recite it immediately after Shabbat, when we are joyful and nicely dressed . However, if there is reason to fear that waiting until Saturday night will cause us to miss the opportunity to say the blessing, it is preferable to say it on a weeknight (Shulchan Aruch, Rama 426:2).
The custom is not to recite Birkat HaLevanah on Friday night, in order to avoid mingling the joy of Shabbat with that of Birkat HaLevanah. However, if there is reason to fear that one will miss the blessing if he does not say it on Friday night, he should recite it then (Rama 426:2, Mishna Berura 12).
As we already learned, the moon alludes to Knesset Yisrael (the Assembly of Israel). Knesset Yisrael is like a bride before God, and “she” renews and purifies herself every month, just like a bride does for her husband. This strengthens the bond between Knesset Yisrael and HaKadosh Baruch Hu. And when all of the world’s flaws are remedied, everyone will recognize the special relationship that exists between Israel and the Holy One Blessed be He, as it says, “Like a bridegroom rejoices over a bride, so will your God rejoice over you” (Yeshayahu, 62:5). Therefore, a custom developed to dance and sing after Birkat HaLevanah, just as at a wedding. Along the same lines, there is a custom to raise up a bit when saying, “Just as I dance before You…” (Rama 426:2).
Since we must say the blessing joyously, we do not to recite it before Tish’a B’Av – because of our mourning over the Temple’s destruction – nor before Yom Kippur, due to our anxiety over the upcoming Day of Judgment. We do say it, however, immediately after Yom Kippur, even though we have not yet eaten, because we are joyous over having had the privilege to stand before God in penitence. It is proper to postpone Kiddush Levanah until the night after Tish’a B’Av, or until people have had a chance to eat and drink and leave their state of mourning (Rama 426:2). However, if it will be difficult to gather a minyan later on, a congregation may sanctify the moon immediately after the fast is over (Mishna Berura 426:11, Sha’ar HaTziyun 9; see also below 10:19).
Similarly, one who is sitting shiva should push off reciting the blessing until after the shiva, if possible, because he is grieving, even if he will have to say it alone. If, however, he cannot push it off – because shiva will end after the permissible time to say the blessing – he should say it during his mourning period (Mishna Berura 426:11, Kaf HaChaim 5. The latest time to recite the blessing will be elucidated below, sec. 18).
Shulchan Aruch 426:2; Rabbi Akiva Eiger, ibid.; Biur Halachah, end of s.v. u’mevarech me’umad; Yalkut Yosef 426:11. (The Ben Eish Chai – Shannah Bet, VaYikra 23 – writes that it is proper to recite the blessing with one’s feet together, but the prevalent custom is not to do so.)
Reciting this blessing is like greeting the Shechinah because the Shechinah alludes to Knesset Yisrael (the Assembly of Israel), both being a part of the attribute of Malchut (Kingship). See also the Maharal of Prague’s Chiddushei Aggadot, 3:158, which states that every initial renewal contains an aspect ofreceiving the Shechinah. The author of Biur Halachah (426:2, s.v. u’mevarech me’umad) writes that we recognize God’s greatness through the moon and stars; therefore, saying this blessing is similar to receiving the Shechinah.