The Instructions (GIRM 86) say the purpose of the hymn sung during the Communion procession "is to
express the communicants’ union in spirit by means of the unity of their voices… and to highlight more clearly the 'communitarian nature' of the procession."
The Rite of Communion is an expression and an experience of unity in which the Spirit, through our sharing one Bread and one Cup, actually brings about unity.
We pray in Eucharistic Prayers I and III that, "partaking of the Body and Blood of Christ, we may be gathered into one by the Holy Spirit… that we, who are nourished by the Body and Blood of your Son and filled with his Holy Spirit, may become one body, one spirit in Christ."
In Eucharistic Prayer IV we ask the Father to grant "to all who partake of this one Bread and one Cup that, gathered into one body by the Holy Spirit, they may truly become a living sacrifice in Christ to the praise of your glory."
Father Henri de Lubac, S.J. (Catholicism), pours out a cornucopia of quotations from saints and mystics to recall the tradition that Eucharist is the “sacrament of unity in the Church":
St. John Damascene teaches:
If the sacrament is a union with Christ and at the same time a union of all, one with another, it must give us real unity with those who receive it as we do.
ACTION Ask whether sharing Communion with baptized, separated Christians might help bring about communion.
PRAYER: Make receiving Communion a prayer for unity.