2 Corinthians 13:2-3

13:2 I said before when I was present the second time and now, though absent, I say again to those who sinned previously and to all the rest, that if I come again, I will not spare anyone, 13:3 since you are demanding proof that Christ is speaking through me. He is not weak toward you but is powerful among you.

2 Corinthians 13:10

13:10 Because of this I am writing these things while absent, so that when I arrive I may not have to deal harshly with you by using my authority – the Lord gave it to me for building up, not for tearing down!