Exodus 27:20
And thou shalt command the children of Israel, that they bring thee pure oil olive beaten for the light, to cause the lamp to burn always. And thou shalt command the children of Israel, that they bring thee pure oil olive beaten for the light, to cause the lamp to burn always.
The command was for Israel to bring pure olive oil, beaten for the light, to cause the sanctuary lamp to burn always. The oil was to be supplied continually so the lamp would keep burning and the house of God would have what its service required. That supply was a regular, continual offering meant to keep God's house furnished with what was needed for its service.
The instruction stands among the tabernacle-building specifications that Paul repeated to his fellow workers, showing that the skill, wisdom, and ability employed in that construction came from God and were to honor Him. The continually burning lamp represented God's church shining as a light to the world, with Israel to represent God's great light, a light that was never to become extinct. When Ahaz closed the temple doors and left the lamp unlit, it marked the interruption of the sacred services.
The requirement continues as a present duty to properly supply, care for, and carefully maintain houses of worship, which belong to the Lord. Funds for that upkeep are to be provided by offerings separate from the tithe and must not be taken from the tithe. The tithe is reserved to support the ministers appointed to serve the people.