What is it?
Hanukkah in Hebrew means, "dedication." This holiday, known as the "Festival of Lights" commemorates an actual historical event. That event is the revolt of the Maccabees in Israel against the Selucid Empire, and specifically against Antiochus Epiphanes, the ruler at the time.
After the invasion of the Syrian-Greeks, Antiochus desecrated the Temple, and tried to get the Jews to offer up a pig as a sacrifice to their gods. However the Jews revolted, and routed the Seleucid Empire. Part of restoration was the re-dedication of the Temple by making holy vessels. The story goes that there was found only one vessel of oil for the menorah, that had been dedicated by the high priest that was not violated. It was only supposed to last one night, but lasted 8 nights while new oil was prepared. This is the reason why 8 branch menorahs are used during this time of year.
Why Should Believers Celebrate?
Yeshua Is Our Light
12 Yeshua spoke to them again: “I am the light of the world; whoever follows me will never walk in darkness but will have the light which gives life.”
Just as the menorah represented the presence of G-d in the Temple, Yeshua disperses the darkness of sin in our hearts, through the light of the Holy Spirit. Without His light, we cannot find our way to everlasting life.
Very simple. Yeshua (Jesus) did.
John 10: (22) Then came Hanukkah in Yerushalayim. It was winter, (23) and Yeshua was walking around inside the Temple area, in Shlomo’s Colonnade.
It is not mentioned in the OT, because the invasion of the Seleucid Empire happened between the testament periods.