When Yom Tov falls on Motza'ei Shabbat, we add in the Amida prayer during Arbit the paragraph of "Va'todi'enu." This paragraph speaks of the distinction God draws "Bein Kodesh Le'kodesh" – between different degrees of sanctity. The occurrence of Yom Tov on Motza'ei Shabbat highlights the difference between the sanctity of Shabbat and the sanctity of Yom Tov, and in "Va'todi'enu" we give praise to God for making this distinction. "Va'todi'enu" differs from the paragraph recited on a regular Motza'ei Shabbat, "Ata Chonantanu," which speaks of the distinction God draws "Bein Kodesh Le'chol" – between the sacred day of Shabbat and the weekdays.
If on a regular Motza'ei Shabbat a person forgot to recite "Ata Chonantanu" during Arbit, he does not, generally speaking, repeat the Amida. If, however, one forgot to recite "Ata Chonantanu" and he ate something before reciting Havdala (in violation of the Halacha that forbids eating before Havdala), the Sages imposed a penalty requiring him to repeat the Amida (Shulchan Aruch, 294). The question arises as to whether this applies as well to the "Va'todi'enu" paragraph when Motza'ei Shabbat coincides with Yom Tov. Meaning, if a person forgot to recite "Va'todi'enu" during Arvit when Yom Tov falls on Motza'ei Shabbat, and then he eats before reciting Havdala (which we incorporate as part of the Yom Tov Kiddush), must he repeat the Amida?
The Peri Megadim (Rabbi Yosef Teomim, Poland-Germany, 1727-1792) rules that such a person must, in fact, repeat the Amida, just as in the case of "Ata Chonantanu." However, Chacham Bentzion Abba Shaul (Jerusalem, 1924-1998), in his work Or Le'tziyon (vol. 3, 18:5), disagreed, and distinguished in this regard between "Ata Chonantanu" and "Va'todi'enu." The paragraph of "Ata Chonantanu" was composed by the Anshei Kenesset Ha'gedola ("Men of the Great Assembly," who instituted and composed the daily prayer services), and thus its omission is looked upon with severity. "Va'todi'enu," by contrast, was written later, during the times of the Talmud, by Rav and Shemuel, and hence it is of a lower Halachic stature. Therefore, one who forgets to recite "Va'todi'enu" does not face the same consequences as one who mistakenly omits "Ata Chonantanu," and thus even if he ate before reciting Havdala, he does not repeat the Amida. However, Hacham Ovadia Yoseph in Hazon Obadya Yamim Noraim, rules that one indeed must repeat the Amidah.
When reciting the Havdala on Motza'ei Shabbat that is also Yom Tov, may one use the Yom Tov candles as the candle for the Beracha of "Borei Me'orei Ha'eish" during Havdala?
Chacham Bentzion Abba Shaul ruled that since Yom Tov candles are lit for the purpose of providing light in the home, they are suitable for Havdala, as well, when we recite a Beracha over the light provided by fire.
The question, however, arises as to whether one should bring two Yom Tov candles together when reciting the Beracha of "Borei Me'orei Ha'eish." Generally speaking, Halacha requires reciting this Beracha over an "Avuka," a "torch," or a light consisting of at least two wicks. Seemingly, then, it would be proper to hold two Yom Tov candles together when reciting "Borei Me'orei Ha'eish" on Motza'ei Shabbat that is also Yom Tov, so that the Beracha is recited over an "Avuka."
However, Chacham Bentzion Abba Shaul ruled (in Or Le'tziyon, vol. 3, 18:7) that in this case, one should recite the Beracha of "Borei Me'orei Ha'eish" over a single candle, and should not bring two candles together. Bringing two candles together runs the risk of extinguishing one of the candles, which would constitute a violation of Yom Tov. Therefore, given that many authorities allow reciting the Beracha of "Borei Me'orei Ha'eish" during Havdala over a single wick, it is preferable to rely on those views rather than bring two candles together to form an "Avuka."
Summary: When Yom Tov falls on Motza'ei Shabbat, one adds the paragraph of "Va'todi'enu" in the Arvit service. One who forgets to add this paragraph does not repeat the Amida, even if he mistakenly ate before reciting Havdala. When reciting the Beracha over fire in Havdala on Yom Tov that falls on Motza'ei Shabbat, one may use the Yom Tov candles, and he need not combine two candles together to form a "torch" as we normally require on a regular Motza'ei Shabbat.
