Jesus accomplished all three roles necessary to finish the work on the cross. He was the great high priest who offered the sacrifice. He was the holy one on the throne who received the sacrifice. And he was the sacrifice itself. You and I are in the equation purely by his grace and that’s how we are saved. The only thing necessary to receive salvation is faith. We have no faith of our own so we must ask God to give us the faith to believe and receive the grace of salvation. So even though we are invited into the process, we are not the source of any of the elements necessary for us to be saved. This is how God in Christ saved us single-handedly.