BaMidbar 8:1 - 12:16
And HaShem spoke to Moshe, saying:
Speak to Aharon, and say to him, 'When you light the lamps towards the face of the Menorah shall the seven lamps cast [their] light.'
The lamps should be facing the center of the Menorah. This light on the center shaft is known as "the lamp of the West."
The Menorah out ot be constructed of gold, if at all possible; in the absence of sufficient gold, other metals would be acceptalbe (Sifri Nasso 61).
One must not have more or fewer than the seven lamps prescribed.
The whole Menorah was to be cast in one piece of metal. To make this pont clear the Torah repeated the words "it is to be a (single) casting." Whereas a Menorah of more than one piece would not be acceptable for use, a Menorah which was not of gold would be acceptable.
Peshat - The Menorah with its seven lamps is an allusion to the Torah which is generally known as "or" (light).
Derash - The Menorah with its seven lamps corresponded to the seven fixed stars which orbit the whole globe; the meaning of these words is that these seven fixed stars are perceived as spearate light bodies in the skines exerting their respecitive influences on the creatures in the terrestrial world and providing guidance for our world both by day and by night. The seven lamps on the Menorah were buring around the clock by day and by night just as the seven fixed stars suply their light by day and by night without interruption. The middle lamp represented the sun which is constant in its light and the center of the seven fixed stars. (Tanchuma Beha'alotcha 5)
Sod - The Menorah alludes to all levels of emanations, excellence, superiority. The fact that it was made of a single chunk of gold symbolises the concept of perfect unity. The six "arms" protuding from the center shaft in both directions symbolise the six proliferations from the center line of the diagram of the emanations. The lamp which burned on top of these arms symbolised "insight" an emanation above the lower six and supplied with direct input from the essence of G-d. It is the lamp (light) which is described by Shlomo as (the origin of) man's soul (Mishlei 20:27). It was placed in the south opposite the emanation wisdom. This is the mystical dimension of the statement in Baba Batra 25 that "he who wishes to become rich should turn south."