I have grown to understand that this quote of Christ is very important in terms of the mysteries of the Church: “For where two or three are gathered together in My name, I am there in their midst.”
Why is this so? Because the mysteries of the Church make Christ present, which is seen foremost in the Eucharist. Christ becomes present in the the coming together of people into the His name, which means that the mysteries are realised by the Holy Spirit when the conditions of coming together into the name of Christ are fulfilled together with being of one mind, that is unanimously agreeing with each other into unity. That it is a condition for the fulfilment is that the gathering is not one in the name of Christ where the people are gathered together already assuming the name of Christ, but into that the gathering meets conditions that allows it to be identified by the name of Christ. It is the result of the gathering in unity. This is not exclusive of coming together in the name of Christ nor does it imply that those gathering are not already in the name of Christ but that the coming together of the gathering manifests Christ’s presence in a particular manner as fitting for that coming together.
This is foremost seen in the Divine Liturgy where the people gather together around the icon of Christ, the priest, “according to all and for all (κατὰ πάντα καὶ διὰ πάντα)” that Christ has commanded in various symbols, and “in one mouth and one heart” the people consent with the priest by their “Amen”, thus uniting themselves in unanimous agreement so that Christ becomes present among them by His Spirit and transforms the congregation and gifts into the body of Christ. It is also true in the councils of Bishops that when they come together in unanimous consent in conformity with the Tradition of the Church, that is with the teaching and practice of Christ, then Christ, by the Spirit, becomes present in the council and the judgement of the council becomes His judgement and His judgement becomes that of the council, particularly in terms of binding and loosing. This is also true in marriage when husband and wife are of one mind with each other in conformity with the teaching and practice of Christ then Christ becomes present with them. In the ordination of a Bishop this is also seen with all the Bishops of the region needing to agree with the Metropolitan/Patriarch to the ordaining of the new Bishop then at least two or three come together to ordain, to symbolise this but ideally all should be there and the official minimum is now three. The ordination needs to be in conformity with Tradition hence the promise of obedience of the candidate to the Creed and to the canons. A priest should also be ordained with the consent of all the priests of the diocese and be of suitable life to be a true icon of Christ. In both these cases the people’s consent to the ordination is appropriate. However, where there is discord or not a unanimity of mind or failure to conform to the teaching and practice of Christ, that is coming into His name then the mystery is not effected. Thus, such a Liturgy, Council, ordination and marriage does not make Christ present; although God in His mercy overlooks many minor disagreements, sins etc due to our weaknesses.