“Where Christ is, there is the Catholic Church.” (St. Ignatius of Antioch, d. 107AD)
“Where the Church is, there is the Spirit, and where the Spirit is, there is the Church.” (St. Irenaeus of Lyons, d. 202AD)
In the writings of the post-apostolic fathers and early Patristic writers, there is made a close union between Christ the Word of God and the Holy Spirit. St. Irenaeus describes them as being “the two-hands of God” at work in creation. In the quote below by St. John Chrysostom, we see how closely he identifies the presence of Christ in us with the presence of the Holy Spirit in our lives. To have “Christ in me” is to have the Holy Spirit. Likewise, to have the Holy Spirit abiding in oneself means that Christ is present as well.
“St. John Chrysostom writes, ‘You will ask, “What will happen if Christ is within us?” “If Christ is in you, your body is dead to sin, but your spirit lives unto righteousness” (Rom. 8:10). You see how much evil comes from not having the Holy Spirit within you: death, enmity towards God, the impossibility of pleasing Him by submission to His law, or of belonging to Christ and having Him dwelling in you. Look also how good it is to have the Spirit within you: really to belong to Christ, to have Christ Himself within you, to compete with the angels! For to have a body dead to sin, means to begin to live in eternal life, to carry within you – even here on earth – the pledge of the resurrection and the reassuring power to advance upon the path of virtue.
Note that the Apostle said not only, “the body is dead”, but added, “to sin”, so that you should understand that it is the sins of the flesh, and not the body itself, that is mortified. It is not of the body as such that the Apostle speaks; on the contrary he wants the body, although dead, still to remain alive. When our bodies, in so far as carnal reactions are concerned, do not differ from those that lie in the grave, this is a sign that we have the Son within us, and that in us dwells the Spirit.’ As darkness cannot stand before the light, so all that is carnal, passionate or sinful cannot stand before our Lord Christ and His Spirit.
But as the existence of the sun does not abolish the fact of darkness, so the presence within us of the Son and Spirit does not abolish the existence within us of something that is sinful and passionate, but only takes away its power. As soon as an occasion arises, the passionate and sinful elements step forward and offer themselves to our consciousness and will. If our consciousness pays attention and occupies itself with them, then our will may also turn towards them. But if, at that moment, our consciousness and will pass over to the side of the spirit and turn to our Lord Christ and His Spirit, then all that is carnal and passionate will disappear immediately like smoke before a breath of wind. This means that the flesh is dead, powerless. Such is the general rule of life for true Christians; but they are at different stages.
When someone remains steadfastly with his consciousness and will on the side of the Spirit, in living and tangible union with Christ our Lord in His Spirit, then at that time nothing carnal or passionate can so much as show itself, any more than darkness before the sun or cold before flames. In such a case, the flesh is quite dead and immobile.” (Theophan the Recluse in The Art of Prayer: An Orthodox Anthology, pp 176-177)