An altar is a place of devotion because it is a place of sacrifice and consecration. It is central to worship. In old testament times, an animal would be sacrificed on an altar. This was done for many reasons — sometimes to cover a person’s sins, and sometimes to declare something holy, and sometimes to consecrate or set apart something for special use. It was always done as a recognition of God’s sovereignty over man, as well as a symbolism of man’s devotion to God. The sacrifice on the altar always had to be with something of worth. One time Israel came under the judgement of God partly because of the sin of King David. When David realized his offense, he wanted to build an altar and make sacrifices to remove his sin and stay the hand of God (2 Samuel 24:10-15). A man named Araunah freely offered his property, supplies, and livestock for the purpose of David’s sacrifice. David refused the free offer and instead purchased those things from Araunah, famously declaring that he would not make sacrifices that cost him nothing (2 Kings 24:24).
Occasionally, an altar would fall into disrepair because the people were not using it. And sometimes, an altar would sadly be torn down in favor of another god’s altar. During Elijah’s time, the people of God began to worship the Baals, and began to sacrifice to those gods. They tore down God’s altar. Before defeating the 450 prophets of Baal atop Mount Carmel, Elijah repaired it. He chose twelve stones to represent the twelve tribes of Israel, and used those stones to build a new altar (1 Kings 18:30-40). Perhaps he was trying to symbolically unify his people around a sacrificial altar and properly center their hearts for return to true worship.
Of course, the costliest sacrifice was made by God, when he sacrificed his perfect son on the altar of the cross. This allowed us to never have to make physical sacrifices again (Hebrews 10:10).
Today we sacrifice at the altar terrible things that we have valued. We lay down our sins there. We lay down portions of our lives at the altar that displease God. We even lay down good things that we have valued more than God. We do all of this to consecrate ourselves to his service, and so that his image in us can be restored. Where is your altar? Does it have a central place in your worship? What have you sacrificed on it?