The sacrificial altar is a strange concept for many modern believers, so why did God command His followers to use an altar for sacrifices?

The biblical history of altars.

Most people associate the altar with the Law given to Moses at Mount Sinai. However, altars appear prominently in the earliest parts of the Old Testament:

• Upon exiting the ark, Noah built an altar and placed burnt offerings upon it (Genesis 8:20, NIV).
• When Abraham took Isaac to Moriah in obedience to God’s command, he built an altar on which he would offer his son (Genesis 22:9, NIV).
• Jacob built an altar upon arriving at Shechem after returning from Paddan-Aram (Genesis 33:20, NIV).

The altars God directed Moses to construct.

The most familiar altar in the Old Testament is the one associated with the Tabernacle and, later, the Temple. In fact, there were two altars in both the Tabernacle and the Temple: the burnt-offering altar and the incense altar. The burnt-offering altar was made of wood coated in bronze and located outside the Tabernacle. The incense altar was made of wood covered in pure gold and was located inside the Tabernacle, just outside the Most Holy Place. Both altars were carried over from the Tabernacle to the Temple Solomon constructed in Jerusalem.

The instructions for the "bronze altar" are found in Exodus 27:1-8 (NIV). It was 7 ½ feet long and wide and 4 ½ feet high (5 cubits by 3 cubits). This altar was designed to be transported with the Tabernacle, so it had rings on its corners, with bronze-covered poles inserted through the rings to carry it.

The directions for the incense altar are found in Exodus 30:1-10 (NIV). This altar was 18 inches wide and long and three feet high. While the burnt-offering altar was covered in bronze, the incense altar was covered in pure gold. It also had rings and poles for carrying. Each year, it was purified with blood from the purification offering.

The uses of the altars.

The Hebrew word for "altar" comes from a root meaning "to slaughter as a sacrifice." For this reason, many assume that the altar was where sacrifices were killed. However, in the Old Testament, sacrificial animals were not killed on the bronze altar. The animals were slaughtered near the altar, and then the appropriate parts of the animal were placed on the altar to be burned. Additionally, the bronze altar was used for more than animal sacrifices; grain and drink offerings, as well as incense, were also offered on this altar.

The incense altar, on the other hand, was exclusively for incense. Twice each day, Aaron, and later his successors as high priest, offered incense on this altar (Exodus 30:7-8, NIV). Only incense, prepared according to strict specifications, was ever offered on the incense altar.

The altar also had a protective function. Those seeking asylum would go to the altar and grasp the horns of the altar. Both Adonijah and Joab did this after their rebellion against Solomon (1 Kings 1:51, NIV; 2:28, NIV). Presumably, this related to the altar being in God's "house," where no violence was permitted. This concept of "sanctuary" continued well into the Christian era and is still recognized in principle today with the connection between a "sanctuary" as a place of worship and as a place of refuge extending back to the Old Testament practice of grasping the horns of the altar. This same idea is reflected in the "cities of refuge" designated by Moses (Numbers 35, NIV).

God’s approval of the altars.

God demonstrated His approval of the altars upon the consecration of the Tabernacle by causing His presence to fill it: “When Moses had finished all the work, the cloud covered the meeting tent and the Lord’s glorious presence filled the dwelling” (Exodus 40:33-34, CEB). When Solomon constructed the Temple in Jerusalem, he included a larger altar for burnt offerings—thirty feet long, thirty feet wide, and fifteen feet high (2 Chronicles 4:1, NIV). He also made a gold incense altar (1 Kings 7:48, NIV). When the Temple was dedicated, God once again demonstrated His approval: “As soon as Solomon finished praying, fire came down from heaven and consumed the entirely burned offering and the sacrifices, while the Lord’s glory filled the temple” (2 Chronicles 7:1, NIV).

Clearly, God wanted the Israelites to use the altars He had directed Moses to build. The question is: Why?

Why did God command the use of altars?

First, both the Tabernacle and the Temple were places where God "lived" among His people. Therefore, any sacrifices offered to God would logically take place “at His house”—on the altar He had directed Moses to build. Second, the altar reflected God’s holiness because of the purification rituals prescribed for it. Beyond the initial purification, an annual ritual of reconciliation was commanded to purify the incense altar. Moses also purified the bronze altar by anointing it with oil, as directed by God (Exodus 30:25-28, NIV).

Altars in Christian churches.

Many modern churches have furnishings called “altars.” However, none of these altars is used for sacrificial purposes! In Roman Catholic churches, the altar holds the consecrated bread and wine for the celebration of the Eucharist, connecting it with the idea of sacrifice, as the Eucharist is the remembrance of Christ’s sacrifice for us. In many Protestant churches, the altar is a place of special prayer and consecration. Paul’s challenge in Romans 12:1 (NIV) to “offer yourselves as living sacrifices” supports the practice of such prayers taking place at an “altar.”

Why did God command the use of an altar for sacrifices in the Old Testament? Scripture does not provide a clear explanation; God does not say, “Offer sacrifices at an altar because...” However, His clear directions about the construction and use of the altars give us insight. The altars were used for offerings to God and were holy—cleansed and set apart for God’s use. Their construction, consecration, and use reflect God’s holiness and serve as a reminder to worshipers of His holiness.