Question: What is the appropriate procedure for one has begun to recite the Amida prayer and then suddenly remembers that he has already prayed that specific prayer?
Answer: We have already explained that one may pray a voluntary prayer which one is not obligated to as a voluntary prayer and is tantamount to a donated sacrifice. Nevertheless, we have mentioned the opinion of the Poskim who rule that one should not pray a donated prayer nowadays when concentrating during prayer is quite difficult.
Now, let us discuss our scenario regarding an individual who has begun the Amida prayer and then remembers in the middle of praying that he has already prayed this specific prayer. Indeed, this is a common occurrence by an individual who has a set time to pray Mincha daily, such as at 7:00 PM, and one day this individual happened to be in a place where there was a Minyan praying Mincha at 2:00 PM so he prayed with them. The individual later continues his daily routine which includes going to pray Mincha at 7:00. After beginning to pray, the individual suddenly remembers that he has already prayed. How should the individual proceed? If he continues to pray, he will continue to recite blessings in vain. If he stops praying, this will mean that all the blessings that he has already recited will have been blessings in vain!
The Gemara (Berachot 21a) deals with this situation and states, “Rav Yehuda said in the name of Shmuel: If one was standing in prayer and remembers that he has already prayed, one must stop even in the middle of the blessing.” This means that if one remembers in the middle of the Amida prayer, such as in the middle of the “Refa’enu” blessing, that one has already prayed, one must stop praying immediately, for every blessing one has recited until this point was in error (and one must recite “Baruch Shem Kevod Malchuto Le’Olam Va’ed”). One may not even conclude the blessing one is in the middle of, such as the “Refa’enu” blessing, for the conclusion of the blessing ‘Baruch Ata Hashem Rofeh Cholei Amo Yisrael” is the text of a blessing which includes Hashem’s name in it and it may not be recited in vain.
The apparent question is: We have already explained that according to the letter of the law, one may pray a voluntary/donated prayer, i.e. a prayer of which all blessings are non-obligatory. If so, in our case when one remembers in the middle of praying that one has already prayed this prayer, why not allow the individual to continue at the very least as a donated prayer so that not all of the blessings that he has already recited are considered blessings in vain?
Indeed, the Rishonim disagree regarding this very point, for the Rashba and Ra’avad write that one may, in fact, continue one’s prayer as a voluntary/donated prayer. On the other hand, most of the Geonim and Rishonim disagree and maintain that one must immediately stop praying, for since one has begun this prayer as an obligatory prayer (in error nonetheless), one cannot switch over in the middle of the prayer to make it a donated prayer because prayer is in the place of offerings and we find no such offering that is part obligatory and part voluntary (Tosafot Ha’Rosh quoting Geonim).
Halachically speaking, there is no such thing as a partially voluntary prayer meaning that if one began reciting the Amida prayer because he was under the assumption that it was obligatory, one may no longer continue this prayer as a voluntary/donated prayer based on the ruling of the majority of the Poskim (see Yalkut Yosef, Tefillah, Volume 1, page 202 and on).
Summary: One who has begun reciting the Amida prayer and then realizes that he has already prayed that specific prayer must stop praying immediately, even in the middle of a blessing.
In the next Halacha we shall, G-d-willing, discuss the parameters of this Halacha as it applies to the Arvit prayer.