Shabbat 21b, 23a; sa 673:1. Shabbat 23a states that the preferred way to perform the mitzva is with olive oil, but the Gemara implies that this is so only because its light is more lucid (see Berur Halakha). Therefore, some say that wax is just as good as, if not better than, olive oil, as Darkhei Moshe 673:1 cites. R. Avraham Yitzĥak Kook concurs in Mitzvat Re’iyah §673. However, Me’iri and Kol Bo state that olive oil has an advantage in that it reminds one of the miracle. Many Aĥaronim, including mb ad loc. 4 and ahs ad loc. 1, state likewise. R. Kook and his son R. Zvi Yehuda Kook followed this practice. (Regarding Maharal’s opinion, see Maĥatzit Ha-shekel ad loc. 1, sht ad loc. 4, Kaf Ha-ĥayim ad loc. 18, and Yemei Hallel Ve-hoda’ah 14:21-23.)↩︎

According to the first answer recorded in Shabbat 21b, the time to light is "from shki’a until the market empties of pedestrians." According to the second answer, however, that is how long the candles must be lit. Rif, Rambam, and other Rishonim write that this is a duration of half an hour. sa 672:2, 675:2 rules accordingly. See mb 672:5. However, some Rishonim maintain that one may fulfill one’s obligation if one lights for a shorter period of time and using smaller candles, either because the halakha follows the first answer in the Gemara, or because even though the halakha follows the second answer, once people began lighting indoors there was no longer a need to light for half an hour, which is the amount of time it used to take for people to return from the marketplace (Or Zaru’a, Smag). Therefore, if one does not have enough oil, he should light without a berakha (bhl 672:2, s.v. "ka-zeh"). See Berur Halakha, Shabbat 21b, nn. 4:2, 5; Torat Ha-mo’adim 6:27, 31.↩︎