Today being St. Leo’s feast day, contemplate this from the Tome of Leo:
Accordingly while the distinctness of both natures and substances was preserved, and both met in one Person, lowliness was assumed by majesty, weakness by power, mortality by eternity; and, in order to pay the debt of our condition, the inviolable nature was united to the passible, so that as the appropriate remedy for our ills, one and the same “Mediator between God and man, the Man Christ Jesus,” might from one element be capable of dying and also from the other be incapable. Therefore in the entire and perfect nature of very man was born very God, whole in what was his, whole in what was ours. By “ours” we mean what the Creator formed in us at the beginning and what he assumed in order to restore; for of that which the deceiver brought in, and man, thus deceived, admitted, there was not a trace in the Saviour; and the fact that he took on himself a share in our infirmities did not make him a par-taker in our transgressions. He assumed “the form of a servant” without the defilement of sin, enriching what was human, not impairing what was divine: because that “emptying of himself,” whereby the Invisible made himself visible, and the Creator and Lord of all things willed to be one among mortals, was a stooping down in compassion, not a failure of power. Accordingly, the same who, remaining in the form of God, made man, was made man inthe form of a servant. For each of the natures retains its proper character without defect; and as the form of God does not take away the form of a servant, so the form of a servant does not impair the form of God. . . .
Accordingly, the Son of God, descending from his seat in heaven, and not departing from the glory of the Father, enters this lower world, born after a new order, by a new mode of birth. After a new order; because he who in his own sphere is invisible, became visible in ours; He who could not be enclosed in space, willed to be enclosed; continuing to be before times, he began to exist in time; the Lord of the universe allowed his infinite majesty to be overshadowed, and took upon him the form of a servant; the impassible God did not disdain to be passible Man and the immortal One to be subjected to the laws of death. And born by a new mode of birth; because inviolate virginity, while ignorant of concupiscence, supplied the matter of his flesh. What was assumed from the Lord’s mother was nature, not fault; nor does the wondrousness of the nativity of our Lord Jesus Christ, as born of a Virgin’s womb, imply that his nature is unlike ours. For the selfsame who is very God, is also very man; and there is no illusion in this union, while the lowliness of man and the loftiness of Godhead meet together. . . .
Troparion of St Leo Tone 3
Thou wast the Church’s instrument/ in strengthening the Church’s teaching of true doctrine;/ thou didst shine forth from the West like a sun/ and didst dispel the heretics’ error./ O righteous Leo, entreat Christ our God to grant us His great mercy.
Kontakion of St Leo Tone 3
From the throne of thy priesthood, O glorious one,/ thou didst stop the mouths of the spiritual lions;/ thou didst illumine thy flock with the light of the knowledge of God/ and with the inspired doctrines of the Holy Trinity./ Thou art glorified as a divine initiate of the grace of God.