Question: If one makes a mistake during the Amida of the Shabbat night Arvit prayer and instead of reciting “Ata Kidashta,” one begins to recite “Ata Chonen” which is the continuation of the weekday Amida, how should one proceed?
Answer: As anyone who prays regularly knows, the weekday Amida consists of nineteen blessings, beginning with the “Magen Avraham” blessing followed by the “Mechayeh Ha’Metim” blessing followed by the blessing of “Ata Kadosh.” On weekdays, the “Ata Chonen” follows “Ata Kadosh” whereas on Shabbat, “Ata Kadosh” is followed by a special blessing designated for Shabbat: Either “Ata Kidashta” (during Arvit), “Yismach Moshe” (during Shacharit), or “Ata Echad” (during Mincha).
Rabba bar Avuha’s Reply
The Gemara (Berachot 21a) relates that Rav Nachman said that when he stayed by Rabba bar Avuha, he saw people coming to ask him what the law is if they made a mistake and proceeded to recite “Ata Chonen” as they would during the week during Shabbat prayers. It would seem that they should immediately stop in the middle of the blessing and return to the blessing reserved for Shabbat, such as “Ata Kidashta” and the like.
Nevertheless, Rabba bar Avuha replied that they must first conclude the blessing they had mistakenly begun and only then should they return to the “Ata Kidashta” blessing. The reason for this is because “Ata Chonen” as well as all of the other blessings of the weekday Amida apply to Shabbat as well. However, our Sages exempted us from reciting these blessings in honor of Shabbat, for they did not wish to burden us with long prayers and supplications. Nevertheless, according to the letter of the law, it would have been appropriate to recite all of the weekday blessings.
Thus, if one mistakenly begins the “Ata Chonen” blessing, one must conclude it by reciting “Baruch Ata Hashem Chonen Ha’Da’at” and only then proceed to recite the “Ata Kidashta” blessing. The same applies to any other blessing during which one becomes aware of his error in that one must conclude the current blessing and only then return to “Ata Kidashta,” “Yismach Moshe,” “Ata Echad.”
One Who Errs During Mussaf of Shabbat
On the other hand, if makes a mistake during Mussaf of Shabbat and begins reciting “Ata Chonen,” Maran Ha’Shulchan Aruch (Chapter 268) rules that one should not conclude the current blessing one finds himself in; rather, one should immediately return to the “Tikanta Shabbat” blessing, for the weekday blessings have no bearing to the Mussaf prayer whatsoever. The Rambam, Rabbeinu Yonah, and others rule likewise.
Summary: If one mistakenly continues with the “Ata Chonen” blessing during Shabbat prayers, one must conclude the current blessing one finds himself in and only then return to blessings reserved for Shabbat, namely, “Ata Kidashta,” “Yismach Moshe,” or “Ata Echad.” However, if this happens during the Mussaf prayer of Shabbat, one must immediately return to the “Tikanta Shabbat” blessing without concluding one’s current blessing.