Sanctuary lamp

The passage, which refers to prescriptions for the tabernacle, states: 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.

In the tabernacle of the congregation without the veil, which is before the testimony, Aaron and his sons shall order it from evening to morning before the LORD: it shall be a statute for ever unto their generations on the behalf of the children of Israel.

This is the precedent for the Catholic custom of burning a candle before the tabernacle, which should be immobile and locked to prevent theft and Host desecration, as well as whenever transporting the Sacrament anywhere.

[6] The custom of multiple lights in odd numbers (i.e., three, five, seven, or more) in place of a single lamp has become rarer, though it is still seen in some older Catholic churches and in Eastern Christianity.

[7] A song by Matisyahu called Aish Tamid ("eternal flame") that appears in his albums Shake Off the Dust... Arise (2004) and Live at Stubb's (2006).