As if I would terrify you by my letters (hōs an ekphobein humas dia tōn epistolōn). This use of hōs an with the infinitive is seen in the papyri (Moulton, Prolegomena, p. 167) and it is not an in the apodosis (Robertson, Grammar, pp. 974, 1040). The active of this old compound verb means to frighten, to terrify. Here only in N.T. It is common in the lxx (Job 7:14; 33:16). Note plural (letters) here and cf. 1Co 5:9; 2Co 2:3.