2 Corinthians 10:8-11

8So even if I boast somewhat freely about the authority the Lord gave us for building you up rather than tearing you down, I will not be ashamed of it. 9I do not want to seem to be trying to frighten you with my letters. 10For some say, “His letters are weighty and forceful, but in person he is unimpressive and his speaking amounts to nothing.” 11Such people should realize that what we are in our letters when we are absent, we will be in our actions when we are present.