א אִם הוּא מְסֻפָּק אִם הִתְפַּלֵּל, חוֹזֵר וּמִתְפַּלֵּל, וְאֵינוֹ צָרִיךְ לְחַדֵּשׁ שׁוּם דָּבָר; אֲבָל אִם בָּרִי לוֹ שֶׁהִתְפַּלֵּל, אֵינוֹ חוֹזֵר וּמִתְפַּלֵּל בְּלֹא חִדּוּשׁ; וְעַל יְדֵי חִדּוּשׁ, חוֹזֵר וּמִתְפַּלֵּל בִּנְדָבָה כָּל הַפְּעָמִים שֶׁיִּרְצֶה, חוּץ מִתְּפִלַּת מוּסָף שֶׁאֵין מִתְפַּלְּלִים אוֹתָהּ בִּנְדָבָה; וּבְשַׁבָּת וְיוֹם טוֹב, אֵינוֹ מִתְפַּלֵּל תְּפִלַּת נְדָבָה כְּלָל, וְאִם הִתְחִיל לְהִתְפַּלֵּל עַל דַּעַת שֶׁלֹּא הִתְפַּלֵּל, וְנִזְכַּר שֶׁכְּבָר הִתְפַּלֵּל, פּוֹסֵק אֲפִלּוּ בְּאֶמְצַע בְּרָכָה אֲפִלּוּ יָכוֹל לְחַדֵּשׁ בָּהּ דָּבָר.
1 One Who Is In Doubt If One Prayed, and The Law Regarding a Voluntary [Amidah] Prayer, Containing 4 Se'ifim: If one is in doubt if one prayed [the Amidah], one goes back and prays [the Amidah again], and one does not need to innovate anything new [in the prayer]. But if it clear to one that one prayed, one does not go back and pray [again] without an innovation [i.e. something new added to his prayer]. And by means of [using] an innovation [in one's prayer], one may return and pray as a voluntary [Amidah] as many times as one wants, except for the Musaf prayer [i.e. Amidah], for we do not pray it as a voluntary [Amidah]. And on Shabbat and Yom Tov, one may not pray a voluntary prayer at all. And if one began to pray [the Amidah], under the belief that one did not pray [already], and then [in the middle of one's prayer] remembered that one already prayed [it], one [immediately] stops, even in the middle of a blessing, even if one is able to innovate a new thing into it.