1 I do not doubt, when I consider both your faith and the weakness or wickedness of others, that your mind has been disturbed, for even a holy apostle, full of compassionate love, confesses a similiar experience, saying, “Who is weak, and I am not weak? Who is offended, and I burn not?” Wherefore, as I myself share your pain, and am solicitous for your welfare in Christ, I have thought it my duty to address this letter, partly consolatory, partly hortatory, to your Holiness, because in the body of our Lord Jesus Christ, in which all His members are one, you are very closely related to us, being loved as an honourable member in that body, and partaking with us of life in His Holy Spirit.
Source: Letters (New Advent)