Question: "Why was the fire in the altar to burn continuously (Leviticus 6:13)?"
Answer: Leviticus mentions several times that the fire in the altar was to burn continuously. God wanted a perpetual fire there, and He must have had a reason for it.
Before the giving of the Law, God appeared to Moses “in flames of fire from within a bush. Moses saw that though the bush was on fire it did not burn up” (Exodus 3:2). God chose the appearance of a continuous fire when calling Moses to lead the people out of Egypt to a new land. Later, when God was leading the Israelites out of Egypt, He appeared as a pillar of fire at night (Exodus 13:21–22).
Then came the Law. Outside the tabernacle, the fire for the burnt offering was commanded to be kept burning; never was it to be extinguished. Leviticus 6:13 instructs, “The fire must be kept burning on the altar continuously; it must not go out.” This is mentioned three times in this chapter (verses 9, 12, and 13).
One reason the ongoing fire was so important is that it was started directly by God: “Fire came out from the presence of the LORD and consumed the burnt offering and the fat portions on the altar. And when all the people saw it, they shouted for joy and fell facedown” (Leviticus 9:24). The fire on the altar, therefore, served as a constant reminder of God’s power. It was a gift from heaven. No other source of fire was acceptable to God (see Numbers 3:4).
This fire also represented God’s presence. “God is a consuming fire” (Deuteronomy 4:24). The Shekinah glory was visible in the fire at the altar of burnt offering. This ongoing presence of God reminded the Israelites that salvation is of the Lord. The atonement made at the burnt offering could only be made through Him.
In the New Testament, John the Baptist predicted that the Messiah would baptize with the Spirit and with fire (Matthew 3:11; Luke 3:16). Fire served as a sign of judgment and refining, but it also reminds us of the Holy Spirit’s coming at Pentecost in the form of “tongues of fire” (Acts 2:3).
The continuously burning, divine fire at the altar of burnt offering helped remind the Israelites of the reality of God’s presence and of their need for God. The sacred fire endured throughout the 40 years in the desert and likely beyond that, as tabernacle worship continued until the time of King Solomon and the building of the Jewish temple. When the temple was dedicated, God once again lit the fire on the altar (2 Chronicles 7:1).