On this day Christians remember the 2nd c. Bishop, St. Irenaeus of Lyons. Probably Irenaeus' best known writing is Adversus Haereses ("Against Heresies) where, among other things, he wrote against Gnosticism. In this excerpt he describes how Jesus, by His flesh and blood grants salvation to us in our flesh and blood.
". . . For we have given nothing to Him previously, nor does He desire anything from us, as if He stood in need of it; but we do stand in need of fellowship with Him. And for this reason it was that He graciously poured Himself out, that He might gather us into the bosom of the Father.
"2. But vain in every respect are they who despise the entire dispensation of God, and disallow the salvation of the flesh, and treat with contempt its regeneration, maintaining that it is not capable of incorruption. But if this indeed do not attain salvation, then neither did the Lord redeem us with His blood, nor is the cup of the Eucharist the communion of His blood, nor the bread which we break the communion of His body. 1 Corinthians 10:16 For blood can only come from veins and flesh, and whatsoever else makes up the substance of man, such as the Word of God was actually made. By His own blood he redeemed us, as also His apostle declares, "In whom we have redemption through His blood, even the remission of sins." Colossians 1:14 And as we are His members, we are also nourished by means of the creation (and He Himself grants the creation to us, for He causes His sun to rise, and sends rain when He wills Matthew 5:45). He has acknowledged the cup (which is a part of the creation) as His own blood, from which He bedews our blood; and the bread (also a part of the creation) He has established as His own body, from which He gives increase to our bodies.
"3. When, therefore, the mingled cup and the manufactured bread receives the Word of God, and the Eucharist of the blood and the body of Christ is made, from which things the substance of our flesh is increased and supported, how can they affirm that the flesh is incapable of receiving the gift of God, which is life eternal, which [flesh] is nourished from the body and blood of the Lord, and is a member of Him?— even as the blessed Paul declares in his Epistle to the Ephesians, that "we are members of His body, of His flesh, and of His bones." Ephesians 5:30 He does not speak these words of some spiritual and invisible man, for a spirit has not bones nor flesh; Luke 24:39 but [he refers to] that dispensation [by which the Lord became] an actual man, consisting of flesh, and nerves, and bones—that [flesh] which is nourished by the cup which is His blood, and receives increase from the bread which is His body. And just as a cutting from the vine planted in the ground fructifies in its season, or as a corn of wheat falling into the earth and becoming decomposed, rises with manifold increase by the Spirit of God, who contains all things, and then, through the wisdom of God, serves for the use of men, and having received the Word of God, becomes the Eucharist, which is the body and blood of Christ; so also our bodies, being nourished by it, and deposited in the earth, and suffering decomposition there, shall rise at their appointed time, the Word of God granting them resurrection to the glory of God, even the Father, who freely gives to this mortal immortality, and to this corruptible incorruption, 1 Corinthians 15:53 because the strength of God is made perfect in weakness, 2 Corinthians 12:3 in order that we may never become puffed up, as if we had life from ourselves, and exalted against God, our minds becoming ungrateful; but learning by experience that we possess eternal duration from the excelling power of this Being, not from our own nature, we may neither undervalue that glory which surrounds God as He is, nor be ignorant of our own nature, but that we may know what God can effect, and what benefits man receives, and thus never wander from the true comprehension of things as they are, that is, both with regard to God and with regard to man . . ."
(Irenaeus, Adv. Haer. V, 2, 1-3; source: http://newadvent.org/fathers/0103502.htm)