1,413. Establishing the Holiday

Hilchos Megillah v’Chanukah 3:2

When the Jews defeated their enemies, they entered the Temple. This was on 25 Kislev. They only found one cruse of ritually pure oil with which to light the Menorah; this was only enough for one day. Nevertheless, they were able to light from it for eight days, which was how long it took to crush the olives and produce a new supply of ritually pure oil.

Hilchos Megillah v’Chanukah 3:3

The Sages who lived at that time decreed that the eight days starting from 25 Kislev should be commemorated as days of joy and praise. Candles are to be lit on each of these evenings at the entrance to the Jews’ homes in order to publicize the miracle. These days are called Chanukah and it is prohibited to eulogize or to fast on them, the same as on Purim. Lighting the Chanukah candles is a rabbinic mitzvah, just like the reading the Megillah on Purim.