The reading is from St. Paul's Second Letter to the Corinthians 1:21-24; 2:1-4

Brethren, it is God who establishes us with you in Christ, and has commissioned us; he has put his seal upon us and given us his Spirit in our hearts as a guarantee.

But I call God to witness against me - it was to spare you that I refrained from coming to Corinth. Not that we lord it over your faith; we work with you for your joy, for you stand firm in your faith. For I made up my mind not to make you another painful visit. For if I cause you pain, who is there to make me glad but the one whom I have pained? And I wrote as I did, so that when I came I might not suffer pain from those who should have made me rejoice, for I felt sure of all of you, that my joy would be the joy of you all. For I wrote you out of much affliction and anguish of heart and with many tears, not to cause you pain but to let you know the abundant love that I have for you.