R Ḥiyya bar Ashi said that Rav said: One who lights a Hanukkah light must recite a blessing. And Rabbi Yirmeya said: One who sees a burning Hanukkah light must recite a blessing because the mitzva is not only to kindle the light but to see the light as well.
Ultimately, the Gemara concludes that two blessings are recited on every night of Hanukkah, with an additional blessing recited on the first night. In delineating the different blessings, the Gemara says that one of the everyday blessings that is recited is:
Who has made us holy through His commandments and has commanded us to light the Hanukkah light.
To which the Gemara asks:
And where did He command us?
The mitzva of Hanukkah is not mentioned in the Torah, so how is it possible to say that it was commanded to us by God?
This question is often asked with regard to blessings recited over mitzvot of rabbinic origin. Two answers are offered by the Gemara:
Rav Avya said: The obligation to recite this blessing is derived from the verse: “You shall not turn aside from the sentence which they shall declare unto you, to the right, nor to the left” ( 17:11).
From this verse, the mitzva incumbent upon all of Israel to heed the statements and decrees of the Sages is derived. Therefore, one who fulfills their directives fulfills a divine commandment. Next:
Rav Neḥemya said that the mitzva to heed the voice of the Elders of Israel is derived from the verse: “Ask your father, and he will declare unto you, your Elders, and they will tell you”( 32:7).
Here, the Gemara cites two sources. The first, “You shall not turn aside,” which is both simple and accepted halakha, was sufficient. The Gemara preferred a source from a positive rather than a negative mitzva and therefore cited the verse: “Ask your father” (Rabbi Elazar Moshe Horowitz).