That I may not seem as if I would terrify you by letters. — The logical sequence of thought is: “I say this” (i.e., that my sentence of delivery to Satan will not be a hollow form) “in order that I may not seem to frighten you as with a bug-bear.” This, it is clear from what follows, had been said. (Comp. the sneer in the next verse.) The use of the plural in this verse and that which follows is in favour of the hypothesis of a lost letter being referred to in 1 Corinthians 5:9, but does not absolutely prove it.
Related Commentaries of 2 Corinthians 10:9
2 Corinthians 10:9
9 That I may not seem as if I would terrify you by letters.