Altars (, mizbeaḥ, "a place of slaughter or sacrifice") in the Hebrew Bible were typically made of earth () or unwrought stone (). Altars were generally erected in conspicuous places (; ; ; ; ). The first time the word altar is mentioned and recorded in the Hebrew Bible is that it was erected by Noah, although it does not specify that there was an altar in (). Other altars were erected by Abraham (; ; ;), by Isaac (), by Jacob (; ), by Moses (), and by Saul (1 Samuel 14:35).
After the theophany on biblical Mount Sinai, in the Tabernacle, and afterwards in the Temple in Jerusalem, only two altars are mentioned: the Altar of Burnt Offering and the Altar of Incense.
Altar of burnt offering
The first altar was the Altar of Burnt Offering (mizbeach ha'olah; ), also called the Brasen Altar (), the Outer Altar (mizbeach hachitzona), the Earthen Altar (mizbeach adamah), the Great Altar (mizbeach hagedola) and the Table of the Lord (). This was the outdoor altar and stood in the Court of the Priests, between the Temple and the Court of Israel, and upon which the korbanot (animal and bird sacrifices) were offered. The blood of the sacrifices would be thrown against the base of the altar (; ), and portions of the sacrifices would be burned on top of it (precisely which portions would depend upon the type of sacrifice). Also consumed at the altar would be some of the meat offerings, and the drink offerings (libations of wine) were poured out here. All sacrifices had to be "seasoned with salt" (, ).
A priest officiating at a burnt offering would vest in his priestly vestments before approaching the altar. He would remove the ashes and place them beside the altar. Then he would change his clothing and remove the ashes to a clean place outside the camp (, Cf, ).
In the various utensils used with the altar are enumerated. They were made of brass. (Comp. ; ; ). The altar could not be carved using utensils made of iron or of bronze (), nor were any allowed on or near it, because iron and bronze were used for implements of war. The Altar and its utensils were considered to be sacred, and the priests had to vest and wash their hands before touching them—even so much as removing the ashes from the altar.
According to the Bible, the fire on the altar was lit directly by the hand of God and was not permitted to go out (). No strange fire could be placed upon the altar. The burnt offerings would remain on the altar throughout the night before they could be removed ().
In the tabernacle
The first altar of this type was made to be moved with the Children of Israel as they wandered through the wilderness. Its construction is described in . It was square, 5 cubits in length and in breadth, and 3 cubits in height. It was made of shittim wood, and was overlaid with brass. In each of its four corners projections, called "horns" (keranot), rose up. The altar was hollow, except for a mesh grate which was placed inside halfway down, on which the wood sat for the burning of the sacrifices. The area under the grate was filled with earth. There were rings set on two opposite sides of the altar, through which poles could be placed for carrying it. These poles were also made of shittim wood and covered with brass.
When Moses consecrated the Tabernacle in the wilderness, he sprinkled the Altar of Burnt Offering with the anointing oil seven times (), and purified it by anointing its four horns with the blood of a bullock offered as a sin-offering, "and poured the blood at the bottom of the altar and sanctified it, to make reconciliation upon it" ().
The Kohathites were the Levites who were responsible for moving and setting up the altar. When it was time for the Israelites to move, they removed the ashes from the altar, and spread a purple cloth over it, placed all of the instruments and vessels used in the sacrifices on it, covered it with a blanket of badger skin, and put the carrying poles in place (). After the rebellion of Korah, the bronze censers that were used by the rebels were converted by Eleazar into broad plates used to cover the altar, as a warning that only priests of the seed of Aaron may offer incense before the Lord ().