When Yom Tob begins on Mosa’eh Shabbat, one may not light the Yom Tob candles until the end of Shabbat. Therefore, a woman must recite "Baruch Ha’mabdil Ben Kodesh Le’kodesh" before she lights the Yom Tob candles, unless she recited Arbit with the special insert of "Va’todi’enu," which serves as a kind of "Habdala" and formally ends Shabbat. Those who every week follow the view of Rabbenu Tam, and refrain from Melacha until 72 minutes after sundown, should do so also when Yom Tob begins on Mosa’eh Shabbat, and should not light candles until 72 minutes after sunset.
When Yom Tob falls on Mosa’eh Shabbat, we combine Kiddush and Habdala, and recite the Berachot in the sequence known by the acrostic "Yaknehaz": "Yayin" ("Boreh Peri Ha’gefen" over wine), "Kiddush" ("Asher Bahar Banu…Mekadesh Yisrael Ve’ha’zmanim"), "Ner" (the Beracha over the candle), "Habdala" (the Beracha of "Ha’mabdil Ben Kodesh Le’kodesh"), and "Zeman" ("She’hehiyanu"). We do not recite the Beracha over spices ("Besamim") when Mosa’eh Shabbat is Yom Tob (Mishna Berura 473:3).
The custom in our community is to recite these Berachot while standing. Although we generally sit for Habdala, we nevertheless stand for the recitation of "Yaknehaz," since it is primarily Kiddush, for which we stand.
One may recite the Beracha of "Boreh Me’oreh Ha’esh" over the Yom Tob candles, since they were lit for the purpose of illumination. However, if a Yahrtzeit candle was lit in memory of a departed loved one, it should not be used for the Beracha of "Boreh Me’oreh Ha’esh," since it was not lit for illumination, but to honor the memory of the deceased. If the candle was lit with the intention that the light should be used, then one may recite the Beracha of "Boreh Me’oreh Ha’esh" over it.
In general, it is preferable to recite the Beracha of "Boreh Me’oreh Ha’esh" over an "Abuka" ("torch"), which means two or more wicks holding a single flame. When Yom Tob falls on Mosa’eh Shabbat, there is a practical problem using a conventional Habdala candle, since one may not extinguish fire on Yom Tob, and thus the candle will have to be left burning until it extinguishes. Therefore, if possible, one should prepare before Shabbat a surface with two wicks with some wax underneath them. These wicks should be lit on Mosa’eh Shabbat from an existing flame, and then the Beracha can be recited over this flame, which will naturally extinguish soon thereafter once all the wax has melted. If one did not prepare these wicks before Shabbat, he should recite the Beracha of "Boreh Me’oreh Ha’esh" over one of the Yom Tob candles. One should not combine two candles together for the Beracha, as it is questionable whether it would then be permissible to separate the candles.
On an ordinary Mosa’eh Shabbat, if one forgot to recite "Ata Honantanu" – which is a sort of Habdala – in the Amida in Arbit, he does not have to repeat the Amida, because he will in any event recite Habdala. However, if he then ate before reciting Habdala, Hazal imposed a "penalty" requiring this person to repeat the Amida. When Yom Tob falls on Mosa’eh Shabbat, however, one who forgot to recite "Va’todi’enu" and then ate before Habdala does not have to repeat the Amida. This is the ruling of Hacham Bension Abba Shaul (Israel, 1923-1998), who explains that whereas "Ata Honantanu" was established by the Ansheh Kenesset Ha’gedola (Men of the Great Assembly), and is thus considered part of the prayer, "Va’todi’enu" was established later, during the time of Rav and Shemuel. As such, "Va’todi’enu" is not an integral part of the Amida, and therefore the "penalty" that applies to one who forget to recite "Ata Honantanu" does not apply to one who forgot to recite "Va’todi’enu." Needless to say, however, one must make every effort to remember to recite "Va’todi’enu" and not to eat before reciting the combination of Kiddush and Habdala.
