From the Office of Readings in today’s Liturgy of the Hours, an excerpt from a letter by Pope St Leo the Great:
To pay the debt of our sinful state, a nature that was incapable of suffering was joined to one that could suffer. Thus, in keeping with the healing that we needed, one and the same mediator between God and men, the man Jesus Christ, was able to die in one nature, and unable to die in the other. [… ]
One and the same person – this must be said over and over again – is truly the Son of God and truly the son of man.