During the eight days of Ḥanuka, we read the Tora in the morning. Now, what Biblical text was chosen by the Rabbis to be read on Ḥanuka and why?
Let me first explain the question. On every Jewish Holiday we read in the Tora a portion corresponding to that specific Holiday. During the eight days of Pesaḥ, for example, we read eight Tora portions alluding to the Exodus from Egypt, the Miṣvot of Pesaḥ, the Pesaḥ sacrifice, etc. But the events of Ḥanuka happened around the year 160 BCE, and were not recorded in the Tanakh (Hebrew Bible). The Rabbis, therefore, had to choose a Biblical text to be read, which somehow will be related to Ḥanuka.
Our Rabbis chose the section of Naso in the book of baMidbar ('In the desert'), dealing with the inaugural offerings of the tribal leaders at the time of the dedication of the mizbeaḥ (=altar of the Tabernacle).
Why?
1. Ḥanuka means 'inauguration', and it remind us that once the Greeks were defeated, the Jews rededicated the altar --which had been defiled by pagan offerings-- to HaShem. The Parasha we read is also about the dedication of the mizbeaḥ in the Tabernacle (zot Ḥanukat hamizbeaḥ).
2. In the dessert, the Tabernacle was completed on the 25 of Kislev. The same day we celebrate Ḥanuka.
3. On the last day of Ḥanuka, we read in beha'alotekha the paragraph dealing with the lighting of the Menora, which remind us of the miracle of the oil.
4. Me'am Lo'ez brings an additional reason. The tribe of Levi did not participate of the offerings at the time of the dedication of the altar, narrated in the Tora. During Ḥanuka, however, the Ḥashmonayim --Cohanim descendants of the tribe of Levi-- were the ones who recovered and rededicated the altar.
"The Macabees realized that there is a time to fight" ,by Rabbi Benjamin Blech, from Aish.com