The Sufferings of Christ are not in Christ alone.

A commentary on Psalm 61 by St Augustine

Jesus Christ is one man, head and body; the saviour of the body and the members of the body are two in one flesh and in one voice and in one suffering; and, when this sinful world shall have passed away, in one rest. So the sufferings of Christ are not in Christ alone; indeed there are no sufferings of Christ except in Christ.  If you understand Christ to be the head and the body, there are no sufferings of Christ save in Christ; but if by Christ you understand the head alone, the sufferings of Christ are not in Christ alone. For if the sufferings of Christ were in Christ alone, that is, in the head alone, why should one of his members, the apostle Paul, speak of making up in his flesh what is lacking in the sufferings of Christ?  So if you are among the members of Christ, whoever you are, whether you hear these words or not (but you do hear, if you are among the members of Christ), whatever you suffer from those who are not among the members of Christ was lacking in the sufferings of Christ.  It is being added, because it was lacking; you are filling up the measure, not causing it to overflow. You are suffering as much as was to be contributed from your sufferings to the whole suffering of Christ, who suffered as our head, and suffers in his members, that is, in ourselves.  To this common republic of ours, so to say, each of us according to his measure pays what he owes, and we contribute as it were a quota of suffering according to the powers that we possess. The storehouse of all men’s sufferings will not have been filled until the world has come to an end.  Do not think, brothers, that all just men who have suffered persecution from the wicked, even those who were sent before the Lord to foretell his coming, do not belong to the members of Christ. God forbid that he who belongs to the city that has Christ for its king should not belong to the members of Christ.  Therefore that whole city speaks, from the blood of Abel the just to the blood of Zechariah. And after that, one city speaks, from the blood of John, through the blood of the apostles and martyrs, and through the blood of the faithful people of Christ.