‘By natural reason man can know God with certainty, on the basis of his works. But there is another order of knowledge, which man cannot possibly arrive at by his own powers: the order of Divine revelation (Vatican Council I: Dei Filius). Through an utterly free decision, God has revealed himself and given himself to man. This he does by revealing the mystery, his plan of loving goodness, formed from all eternity in Christ, for the benefit of all men. God has fully revealed this plan by sending us his beloved Son, our lord Jesus Christ, and the Holy Spirit.’ (The Catechism of the Catholic Church)

‘Thus the Incarnation of the Son of God is the real basis for the divine adoption of the human race, and likewise conducts that adoption to a consummation that is unique in its sublimity. It is the bridge leading to the extension of the divine Trinitarian fatherhood to the race. This fatherhood is not merely imitated in God’s relationship to man, out of sheer grace, but is joined to man substantially; and it is only as a result of this substantial union with man that its imitative force can come into play. The Incarnation sets up a real continuity between the Trinitarian process and the human race, in order that this process maybe prolonged in the race. The Incarnation raises the human race to the bosom of the eternal Father, that it may receive the grace of sonship with all its implied dignities and rights by a real contact with the source, rather than by a merely gratuitous influx from without.’ (Fr. Joseph Matheus Scheeben: The Mysteries of Christianity)

‘Gathering up the first fruits of nature, the Lord received the body of all the faithful in His body, and the souls of all the faithful in one soul, through he unity of nature and the grace of justification. Thereby He took to himself the whole Church in a marriage of perpetual incorruptibility.’
(St. Fulgentius: Ad Thrasam)

‘The nuptial chamber of the bridegroom was the womb of the Virgin, for in that virginal womb were the bridegroom and the bride, namely the Word and the Flesh […]. Therefore now they are not two, but one flesh […]. To that flesh is joined the Church, and thus arises the whole Christ, head and body.’
(St. Augustine of Hippo: In epist. Ioannis)

The moral consequences of this wonder: ‘We are to keep our own persons and our own bodies holy and unsullied, since they are members of Christ, since they belong to Christ and are sanctified by the nobility of His person (1 Cor. 6:15).A profanation of our body is henceforth not only a profanation of our own, but of Christ’s person (Ibid.). And in general, it is not only we who suffer, but Christ suffers in us, with sufferings that resemble those He sustained in His own humanity (Col. 1:24, according to the best exegesis). (Fr. J.M. Scheeben: Mysteries of Christianity)

‘The Son of God assumed the nature of flesh common to all; having thus become the true vine, He contains within Himself the entire race of the offspring. […] It is manifest to all that they share in the body and the kingdom of God; for the Word was made flesh and dwelt amounts us, that is, He took to Himself the nature He of the whole human race.’
(St. Hilary of Poitiers: IN Psalmum 51 # 16)