Catechesis: Righteousness of Faith

Even if Christ had been conceived and born without sin by the Holy Spirit and had fulfilled all righteousness in His human nature alone, and yet had not been true and eternal God, this obedience and suffering of His human nature could not be credited to us for righteousness. Also, if God’s Son had not become man, the divine nature alone could not be our righteousness. Therefore, we believe, teach, and confess that the entire obedience of Christ’s entire person (which He offered to the Father for us, even to His most humiliating death on the cross) is credited to us for righteousness. For the human nature alone, without the divine, could not by obedience or suffering make satisfaction to eternal, almighty God for the sins of all the world. However, the divinity alone, without the humanity, could not meditate between God and us.—FC SD III:56