Keep the Light Burning for the Lord
Exodus 27:21 (ESV) … “In the tent of meeting, outside the veil that is before the testimony, Aaron and his sons shall tend it from evening to morning before the Lord. It shall be a statute forever to be observed throughout their generations by the people of Israel.”
“Aaron and his sons shall tend it from evening to morning before the Lord” This is the first mention of the priesthood which is sort of an introduction to the next chapter which details the priesthood. Aaron and his sons were the first and foremost priests and ministers in the Tabernacle. It was their duty to keep the light shining. Likewise God’s preachers are to keep the light shining. The pulpit should shine forth the glorious truths of the Word of God. Unfortunately, many preachers do not illuminate their people spiritually by their preaching.
“It shall be a statute forever to be observed throughout their generations by the people of Israel” (Exodus 27:21). This matter of providing oil for the lamps was a perpetual thing. The lamps were to ever be shining. The people were, therefore, to ever be providing the oil for the lamps. Thus the giving was to have a perpetual commitment. Many saints forget this perpetual commitment to service, to the maintaining of God’s work. Often churches die because the people lose their commitment to the work. If the light goes out in the work of a church, it is often because the people have stopped maintaining the ministry and the work of the church. We want God to always take care of us. Is it then unreasonable that we are commanded to be perpetual in our service? 
 Butler, J. G. (2008). Analytical Bible Expositor: Exodus (p. 234). Clinton, IA: LBC Publications.