“Christ for us,” or Christ our Substitute, is the gospel or glad tidings of great joy which apostles preached, and which we can tell, even in these later days, to the sons of men as their true hope. The good news which we bring is not of what we are commanded to do in order that God may be reconciled to us, but of what the Son of God has done instead of us. He took our place here, on earth, that we might obtain His place in heaven. As the Perfect One, in life and in death, as the Doer and the Sufferer, He is presented to us that we may get the complete benefit of that perfection so soon as we receive His gospel. All our imperfection, however great, is lost in the completeness of His perfection, so that God sees us not as we are, but as He is. All that we are, and have done, and have been is lost sight of in what He is, and has done, and has been. “He who knew no sin was made sin for us, that we might be made the righteousness of God in Him.”
“Instead of Me”, in Horatius Bonar, How Shall I Come?