Mi Yodeya is a question and answer site for those who base their lives on Jewish law and tradition and anyone interested in learning more. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Many times in Halacha we find that one should repeat if forgetting something. For example, on Rosh Chodesh (by Shacharis or Mincha), one must repeat Shemonah Esrei if s/he forgot Yaaleh Veyovo. On shabbos one must repeat Bentching if forgot Retzei. Etc...

Why is this necessary? What does it accomplish? And, doesn't it come under possible Brocho l'vatalahs?

share|improve this question
up vote 5 down vote accepted

The basic idea, as I understand it, is that if these parts were omitted, it's a case of meshaneh mimatbeya shetav'u chachamim - altering the fundamental text that the Sages instituted for the prayers. This itself invalidates the prayer.

So for example, the correct text of Shemoneh Esreh on Rosh Chodesh is supposed to include Yaaleh Veyavo. If one leaves that out, then, effectively the person has not said Shemoneh Esreh properly - it would be as though they omitted one or more of the regular blessings.

There are some cases where it's questionable where one should repeat the prayer because of such an omission (because there is the counterbalancing concern of a berachah levatalah, a blessing in vain, as you noted). In some such cases, the posekim recommend repeating Shemoneh Esreh as a voluntary (nedavah) prayer, which one is anyway permitted to do (see, for example, Taz to Orach Chaim 118:2 and 582:1).

share|improve this answer
Is it not the case that we do not do Tefillos Nedavah Today? – SimchasTorah Jun 14 '10 at 4:00
That's what Chayei Adam (27:17) says. However, Mishnah Berurah (Beur Halachah 107:1) strongly disagrees. He says that while it is true (per Shulchan Aruch ibid. :4) that in order to pray Tefillas Nedavah one must be certain that he is able to concentrate properly throughout all of it, this does not apply to a TN done because of uncertainty as to whether one recited the appropriate additions to Shemoneh Esreh, and one may (or should) do so even if it may be difficult to have kavvanah throughout all of it. – Alex Jun 14 '10 at 4:40
Sorry but I am Guessing TN is Tefillas Nedavah? – SimchasTorah Jun 14 '10 at 5:07
Yes, that's correct. – Alex Jun 14 '10 at 19:20

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.