The mitzva of lighting the Chanuka menora is derived from the menora that stood in the Holy Temple in Jerusalem. However, there is one important difference between that menora and the one we light in our homes: the menora in the Holy Temple consisted of seven branches, whereas the Chanuka menora has eight.
In order to understand why, let’s put the miracle of Chanuka in historical context:
The miracle of Chanuka took place after an extended period of time in which the menora was not lit. It was impossible to do so, as the Greeks had issued harsh decrees forbidding the Jews to learn Torah and observe its commandments.
When G-d granted the Jewish people the strength to prevail over their enemies, it became necessary to perform an act that would bring an additional measure of light to make up for the deficit the darkness had caused. The Chanuka menora would thus consist of eight lights instead of seven.
This teaches an important point:
Above and beyond the fact that every Jew can transform his home into a “Holy Temple” by lighting the Chanuka menora in commemoration of the ancient miracle, by lighting eight candles he causes an even greater light to shine than existed in the Holy Temple!
In exile, the Jewish people is “weak” and “few in number,” while the nations of the world are “strong” and “many.” Yet the miracle of Chanuka shows that even in a time of great darkness it is possible to overcome all impediments – even meriting a greater measure of light than existed before.
In the merit of observing the mitzva of the Chanuka menora may we very soon see the “lights of Zion” in the Third and eternal Holy Temple, with the coming of Moshiach.