“For since man is most properly understood (or, if that cannot be, then, at least, believed) to be made in God’s image, no doubt it is that part of him by which he rises above those lower parts he has in common with the beasts, which brings him nearer to the Supreme. But since the mind, itself, though naturally capable of reason and intelligence, is disabled by besetting and inveterate vices not merely from delighting and abiding in, but even from tolerating His unchangeable light, until it has been gradually healed, and renewed, and made capable of such felicity, it had, in the first place, to be impregnated with faith, and so purified. And that in this faith it might advance the more confidently towards the truth, the truth itself, God, God’s Son, assuming humanity without destroying His divinity, established and founded this faith, that there might be a way for man to man’s God through a God-man.” —Augustine, The City of God
“The incarnation means that he who never began to be in his specific identity as Son of God, began to be what he eternally was not. We must appreciate the historic factuality and temporal occurrence of the incarnation and the sustained contrasts involved. The infinite became the finite, the eternal and supratemporal entered time and became subject to its conditions, the immutable became the mutable, the invisible became the visible, the Creator became the created, the sustainer of all became dependent, the Almighty infirm. All is summed up in the proposition, God became man. The title ‘God’ comprehends all that attributes that belong to God and the designation ‘man’ all the attributes that are essentially human.” —John Murray, “The Person of Christ”
In order for Jesus to be Jesus (meaning “Yahweh is salvation”) He has to be Immanuel (meaning “God with us”).
When the angel commands Joseph to name the child “Jesus”, he also gives him the reason why, “for He will save His people from their sins.” This is an allusion to Psalm 130:8. In this Psalm the “He” who redeems Israel from his iniquities is Yahweh. Only God can forgive sins ultimately. It is His prerogative; He is the most offended party (Psalm 51:4). You do not have the right to forgive a debt against someone else. The scribes theology was sound when they questioned, “Who can forgive sins but God?” (Mark 2:1-11).
In the 11th century Anslem of Canterbury wrote an important book titled, Cur Deus Homo, loosely translated, Why the God-Man? Why did Jesus have to be Immanuel to deal with sins? Why must the second person of the Trinity take on human flesh? His answer, in short, is that in sin we incur a debt that only man ought to pay and only God can pay. Thus, in order to pay this debt, a God-Man is needed.
In creation, the law, and our conscience we know God above us and against us. Only in the gospel do we know God for us and with us—God incarnate, born of a virgin, truly man, truly God—with us.
Christ, by highest Heav’n adored;
Christ the everlasting Lord;
Late in time, behold Him come,
Offspring of a virgin’s womb.
Veiled in flesh the Godhead see;
Hail th’incarnate Deity,
Pleased with us in flesh to dwell,
Jesus our Emmanuel.
– Hark! the Herald Angels Sing by Charles Wesley