In the United States we begin praying for rain by reciting vesein tal u’matar in the berachah of Bareich Aleinu in Shemoneh Esrei on December 5.
If someone does not say vesein tal u’matar, saying “vesein berachah” instead, he must repeat the entire Shemoneh Esrei if he already concluded saying Shemoneh Esrei. It is as if he didn’t daven Shemoneh Esrei at all. If someone accidentally does not daven at all, he must daven Shemoneh Esrei twice at the following tefillah. Therefore, if someone did not say vesein tal u’matar and only remembers that he did not do so at the next tefillah, he must daven Shemoneh Esrei twice.
If someone remembers during Minchah that he did not recite ya’aleh veyavo during Shacharis, he must similarly daven Shemoneh Esrei twice during Minchah. Tosfos (on Berachos 26b) says that if someone forgets to say ya’aleh veyavo at Minchah on a one-day Rosh Chodesh (or on any other day that we recite ya’aleh veyavo followed by a day on which we don’t) he should not repeat Shemoneh Esrei during Ma’ariv since it no is longer Rosh Chodesh and can no longer say ya’aleh veyavo. Tosfos explains that he does not have to repeat Shemoneh Esrei since he has already davened Shemoneh Esrei; he simply missed the additional prayer of ya’aleh veyavo. The only reason to repeat Shemoneh Esrei would be to say ya’aleh veyavo; however, since he will not be able to recite ya’aleh veyavo during Ma’ariv (since it is no longer Rosh Chodesh), he should not repeat Shemoneh Esrei at all.
Rav Chaim Soloveitchik (stensils, siman 1) says that the halacha regarding ya’aleh veyavo does not apply to a person who forgets to recite vesein tal u’matar on Friday at Minchah. In other words, even though he won’t be able to say vesein tal u’matar at Ma’ariv on Shabbos – as the berachah of Bareich Alenu is not recited on Shabbos – he must nevertheless daven Shemoneh Esrei twice at Ma’ariv.
Rav Chaim explains that forgetting to say vesein tal u’matar is different than forgetting to say ya’aleh veyavo. When a person forgets to say ya’aleh veyavo, he has fulfilled his davening obligation; he merely left out an extra prayer, ya’aleh veyavo. In contrast, when a person forgets to say vesein tal u’matar, he essentially has not said the berachah of Bareich Aleinu and has therefore not fulfilled his davenng obligation. Vesein tal u’matar is not an extra prayer inserted into Shemoneh Esrei; it is part of one of the 18 berachos.
So, if a person does not recite vesein tal u’matar, he has not fulfilled his davening obligation and is considered to have not davened at all. As a result, he must daven Shemoneh Esrei twice at Ma’ariv on Shabbos even though he won’t be reciting vesein tal u’matar in that Shemoneh Esrei.
Many have asked the following question on Rav Chaim’s ruling: The Gemara (Berachos 29a) says that if someone does not mention vesein tal u’matar in its proper place (i.e., in the berachah of Bareich Aleinu), he can say it in the beracha of Shomeia Tefillah. This halacha is codified in the Shulchan Aruch (Orach Chayim 117:5). If vesein tal u’matar is part of the berachah of Bareich Aleinu how can one recite it in a different berachah?
Perhaps we can answer this question by looking at another halacha: If a person remembers that he forgot to say vesein tal u’matar after he has passed the berachah of Shomeia Tefillah but before he has completed Shemoneh Esrei, there is a machlokes Rishonim as to where he must return to in Shemoneh Esrei – to Bareich Aleinu, or to Shomeia Tefillah.
Tosfos (on Ta’anis 3b) says that he should return to Shomeia Tefillah while the Rambam (Hilchos Tefillah 10:9) and the Shulchan Aruch say that he must return to Bareich Aleinu.
It seems that the Rishonim who maintain that one should return to Shomeia Tefillah do not believe that vesein tal u’matar is part of the actual berachah of Bareich Aleinu. They believe that it is an added request (bakashah) that can be inserted either in the berachah of Bareich Aleinu or the berachah of Shomeia Tefillah. Therefore, when a person realizes that he did not say vesein tal u’matar and has already passed the berachah of Shomeia Tefillah, he should go back to the nearest berachah where he may recite this request, namely Shomeia Tefillah.
However the Rambam and Shulchan Aruch, who maintain that one should go all the way back to the berachah of Bareich Aleinu, seemingly are of the opinion that vesein tal u’matar is part of the berachah of Bareich Aleinu (which is the basis of Rav Chaim’s ruling). Therefore, they say that one should return to Bareich Aleinu even though Shomeia Tefillah is closer.