‘If He Didn’t Say, He Must Repeat’
Our sugya is the source for one of the most well-known laws in Hilchos Tefillah. If a person forgets to say Ya’aleh V’yavo in Shemoneh Esreh on Rosh Chodesh or Chol HaMoed, he must repeat Shemoneh Esreh (Shulchan Aruch, Orach Chayim 422:1).
If he noticed his mistake before beginning Modim, he should recite Ya’aleh V’yavo immediately. If he noticed it any time between the beginning of Modim and the end of Shemoneh Esreh, he should return to Retzei and proceed from there.
A Different Mistake Each Time
What if a person forgot Ya’aleh V’yavo, repeated Shemoneh Esreh, and then realized that he recited “Morid Hagesehem” in place of “Morid Hatal” the second time around? Should he repeat Shemoneh Esreh yet again?
Did He Or Did He Not?
At the heart of this question is how our Sages view a tefillah without Ya’aleh V’yavo (or any other insertion whose omission requires one to repeat Shemoneh Esreh). Is it regarded as not having been said at all? Or is it like it was said, but the person must still repeat Shemoneh Esreh to recite the omitted insertion?
If the former, then both the first tefillah and the second tefillah don’t count since they both lacked a crucial insertion, and therefore the person must daven a third time. However, if we consider each tefillah to be a proper tefillah despite the omissions, each tefillah completes what the other lacked, and the person need not daven again.
Many poskim, in fact, rule that the person doesn’t have to daven again (Gur Aryeh Yehudah Orach Chayim 17; Mekor Chaim 108; Birkas Habayis 17:29), but others rule that he must (Mateh Efraim 582:21, Magen Giborim 104, Elef Hamagen s.k. 9; Resp. Likutei Tzvi 10; Resp. Maharshag Orach Chayim 1:52).
Will This Time Be Any Better?
The author of Yagel Yaakov (Orach Chayim 23) argues that even if we consider both tefillos invalid, we should not instruct the person to daven a third time. If he erred twice, he will most likely err a third time. Only if the person is certain he won’t err again should he daven again.
Contemporary poskim (Levushei Mordechai Tinyana, Orach Chayim 12; Resp. Har Tzvi Orach Chayim 1:54; Minchas Yitzchak 10:40) suggest that a person should daven a third time and make a condition that if he is required to daven again, he intends to fulfill his obligation with this third tefillah, and if he is not required to daven again, his tefillah should be considered a voluntary tefillah. That way, both opinions are satisfied.