The brazen altar was the place of substitution for Israel. It was a figure of the cross of Christ. In the Old Testament economy, the sacrificer (one making the offering) had to identify himself with the sacrifice (animal) and be represented by a priest. Under the New Covenant, we must identify ourselves with Jesus in his death. He is our substitutionary lamb. His death was substitutionary. He died in our place. And He is our Great High Priest that represents us.