SINCE communion of the mysteries is not permissible to all simply, likewise he [the priest] himself does not summon everyone, but taking the life-giving bread and displaying it, he calls the worthy who are about to receive it, for them to partake of it:
Holy things (he says) for the holy ones,
as if to say:
See, this is the bread of life which you are looking it. So those about to receive should perform their sacred duties, but not everyone, only if he is holy. For holy things are put at the disposal of holy people alone.
But in this context, he calls “holy” those who are perfect in the virtues, and also such as are pressing onward to this perfection, yet still lack something.
For nothing prevents even such people from being sanctified by participation in the holy mysteries, and in this respect being saints, just as the whole Church is called “holy”, and the blessed Apostle writes to the whole people: Holy brethren (he says), ye are partakers in a heavenly calling.
They are called “holy” because of the holy thing in which they partake, and by which they share communion of body and of blood. For being members of that body, flesh of his flesh, bone of his bone, so long as we remain united to him and keep guard on our harmony with him, we live by drawing down life and sanctification from that Head and Heart, through the mysteries.
St Nicholas Cabasilas, “A Commentary on the Divine Liturgy”, §36. Original at Nektarios.gr.
PRESERVE my soul, for I am holy; save thy servant, O God, who hopes in thee. Pity me, O Lord: for to thee will I cry all the day. Rejoice the soul of thy servant: for to thee, O Lord, have I lifted up my soul.
For thou, O Lord, art kind, and gentle; and plenteous in mercy to all that call upon thee. Give ear to my prayer, O Lord; and attend to the voice of my supplication. In the day of my trouble I cried to thee: for thou didst hear me.
Psalm 85: 2-7.