Why would an altar, a place meant for sacrifice, need atonement itself? It wasn't just a piece of furniture, but a focal point of sin's reality.
After ministering within the Holy of Holies and the Holy Place, the high priest emerges to the altar. This isn't just any altar; it's the altar 'before the LORD,' a place constantly exposed to sin's effects through the sacrifices offered there. Even sacred objects can become tainted by the sin they are meant to address.
A Place Implicated by Sin
Think of it this way: every sin offering brought to this altar represented the people's unholiness. While the altar itself was consecrated, the cumulative weight of sin's presence meant it too needed cleansing. This step highlights that everything in God's presence, even the instruments of worship, must be purified from the defilement that sin brings.