Intercommunion, that is to say participating with heretics in the Holy Sacraments, and especially in the Holy Eucharist, is the most shameless betrayal of our Lord Jesus Christ, Judas’ betrayal. It is especially the betrayal of the whole of the one and unique Church of Christ, of the Holy Tradition of the Church. One would have to rid oneself of one’s Christlike way of thinking and one’s conscience before the various sacraments, before their holy meanings, and the holy commandments in order to do this.
First of all we would have to ask ourselves on what Ecclesiology and on what Theology of the Church is “intercommunion” based? This is because all of Orthodox Theology is not founded on or based on “inter-communion,” but upon the theanthropic reality of communion, that is to say upon theanthropic Communion itself. (cf. 1 Cor. 1: 9; 10: 16-17; 2 Cor. 13: 13; Heb. 2: 14; 3: 14; Jn. 1: 3) The idea of inter-communion is contradictory in itself and totally inconceivable for the Orthodox Catholic conscience.
The second fact, indeed a sacred fact of Orthodox faith, is the following: In Orthodox teaching about the Church and the Sacraments, the single most unique mystery is the Church itself, the Body of the God-man Christ, so that she is the only source and the content of all divine Sacraments. Outside of this theanthropic and inclusive Mystery of the Church, the Pan-Mystery itself, there are no and cannot be any “mysteries”; therefore, there can be no inter-communion of Mysteries. Consequently we can only speak about Mysteries within the Context of this unique Pan-Mystery which is the Church. This is because the Orthodox Church, as the Body Christ, is the source and the foundation of the Sacraments and not the other way around. The Mysteries, Sacraments, cannot be elevated above the church, or examined outside the Body of the Church.
Because of this, in accordance with the mind of the Catholic Church of Christ, and in accordance with the whole of Orthodox Tradition, the Orthodox Church does not recognize the existence of other mysteries or sacraments outside of itself, neither does it recognize them as being mysteries, and one cannot receive the sacraments until one comes away from the heretical “Churches,” that is to say the pseudo-Churches, through repentance to the Orthodox Church of Christ. (Orthodox Faith and Life in Christ, pp. 172-174)