When we recite Birkat Ha’mazon on Shabbat, we add the "Reseh Ve’hahalisenu" paragraph in the third blessing, the section of "Rahem."
The Ba’al Ha’Rokeah (Rav Elazar of Worms, Germany, c. 1176-1238) observes that the letter "Peh Sofit" (the letter Peh at the end of a word) does not appear anywhere in this paragraph. The reason, he explains, is because this letter appears at the end of a number of words associated with calamity and divine anger (such as "Af," "Shesef" and "Kesef"), and so we avoid this letter in the "Reseh" paragraph which speaks of the special day of Shabbat. However, some versions of the text of "Reseh" include the phrase, "Ve’af Al Pi She’achalnu Ve’shatinu" – with the word "Ve’af," which concludes with a "Peh Sofit." It would therefore be more proper to use the alternative text – "Ve’ha’gam She’achalnu Ve’shatinu," which avoids the word "Ve’af."
In another passage in "Reseh," we recite, "Nishbot Bo Ve’nanu’ah Bo." The Kaf Ha’haim (Rav Yaakob Haim Sofer, Baghdad-Israel, 1870-1939) ruled that the word "Bo" in this phrase should be changed to "Bah" when Birkat Ha’mazon is recited on Friday night, such that one should say, "Nishbot Bah Ve’nanu’ah Bah." The reason, he explains, is because in the Amida prayer on Shabbat, the phrase "Ve’yanuhu Bo" which we recite on Shabbat day is recited as "Ve’yanuhu Bah" on Friday night. (Different customs exist regarding the Amida in Minha; the custom in Halab was to recite, "Ve’yanuhu Bam" at Minha, whereas Hacham Ovadia Yosef ruled that one should recite "Ve’yanuhu Bo," just like at Shaharit.) According to the Kaf Ha’haim, just as during the Amida on Friday night we recite "Ve’yanuhu Bah" instead of "Ve’yanuhu Bo," similarly, in "Reseh," we should recite on Friday night, "Nishbot Bah Ve’nanu’ah Bah" instead of "Nishbot Bo Ve’nanu’ah Bo." Hacham Ovadia Yosef, however, disagreed, noting that no Siddurim have such a text in "Reseh," and there is no reason to apply to "Reseh" the rules governing the text of the Amida.
If one’s Se’uda Shelishit meal extended until after dark, such that he recites Birkat Ha’mazon after Shabbat has technically ended, he nevertheless includes "Reseh" in Birkat Ha’mazon. However, the Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909) writes that in such a case, one omits the word "Ha’zeh" from the phrase "Yom Ha’shebi’i Ha’gadol Ve’ha’kadosh Ha’zeh." Since it is no longer Shabbat, one cannot speak of "this day" being Shabbat, and so he omits the word "Ha’zeh."
Summary: Some versions of the "Reseh" paragraph added to Birkat Ha’mazon on Shabbat include the phrase, "Ve’af Al Pi She’achalnu Ve’shatinu," but the more correct text is "Ve’ha’gam She’achalnu Ve’shatinu." If it is already dark when one recites Birkat Ha’mazon after Se’uda Shelishit, he nevertheless includes "Reseh" in Birkat Ha’mazon, but he should omit the word "Ha’zeh" from the phrase "Yom Ha’shebi’i Ha’gadol Ve’ha’kadosh Ha’zeh."
