The Lampstand in the Sanctuary is purposed to bring forth light illuminating all those whose duties are in the Sanctuary of God. Jesus is the flame, the producer of light. The Spirit is the oil, and those who are now believing are to be His “reeds” or His Lampstand through which the oil flows; and the wick that burns is a picture of each individual who bears light. True believers are the very vessel through which it all occurs. This is the measurement of the reed–those through whom the oil perpetually flows. This is the measurement by which humanity will be divided.
The Spirit makes a 3-part distinction in that John is commanded to measure 1) the Sanctuary, 2) the altar, and 3) those who are now worshipping in it?
1) He is contrasting the structure of the Sanctuary of God with the Temple at large.
2) He is contrasting the prayers offered at the altar of incense with the offering of prayers in general.
3) He is contrasting those priests who are now worshipping in the Sanctuary and those who are NOT, and who should be.