Hmmm. you got me on that one. The way I’m interpreting it is that the communion of saints are those christians saved through Christ and with Jesus in heaven.
All the creeds of the christian faith say “I believe in the communion of the saints” so this question has a lot to do with early christian beliefs and how we understand them today.
I’m studying catholicism and what I see is the church of the martyrs and the catacomb christians.
Here is the whole prayer in the beginning of the catholic missal that catholics say when they go into a catholic church.
to Christ before mass
Thou art here Lord Jesus. Thou art going to offer Thy sacrifice Thy joys, Thy sufferings, Thy work, Thy passion, and Thy death. Thou art here Lord, with all Thy Church and its offerings. Our Lady is here, presenting the burning love of her young mother’s heart. The martyrs are here, the martyrs of all the ages, offering their lives; the apostles are here offering their efforts; and all Christians offering their joys and sufferings.
The little ones are here offering Thee simply their first love, and the lads who have just begun to work offering Thee their pride in their labors; engaged couples offering their promises, young husbands and wives offering their love; the mother presents her cradle, the worker his labor, the old man his loneliness, and the dying their lives. An all these offerings of Thy brethren, Lord Jesus, avail only because they are joined to Thine.
And I bring my efforts, my sacrifices, my joys and my sufferings, my entire life since my last Mass, and I bring too, those of the souls with which Thou hast charged me and who are not present. And in order to feel closer to Thee and to all my brethren, in order to increase our mutual love, I am going to receive Thee Jesus.
I am going to receive Thee into a heart which is not humble, but which Thou shalt render as humble as Thyself, into a heart that is hardly pure and which Thou shalt make as pure as Thine; into a heart which is cowardly and which Thou shalt make as brave as Thine; into a heart attached to sin, which Thou shalt purify; into a selfish heart which Thou shalt render loving.
That our love may be greater between my brethren and me … and Thee especially, come Lord Jesus come.
This prayer seems to be an explanation of the “I believe in the communion of saints” belief in the apostles creed.