Verses with the word epistles in the New Testament (2 verses):

2 Corinthians 3:1
Do we begin again to commend ourselves? or need we, as some others, epistles of commendation to you, or letters of commendation from you?

2 Peter 3:16
As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.