Ya, seems the instruction to WRITE is missing from your citation.
See post 87.
How are letters produced without writing:
2 Thessalonians 3:14
If anyone does not obey our instruction in this letter, take special note of that person and do not associate with him, so that he will be put to shame.
2 Peter 3:15-17
15 and regard the patience of our Lord as salvation; just as also our beloved brother Paul, according to the wisdom given him, wrote to you,
16 as also in all his letters, speaking in them of these things, in which are some things hard to understand, which the untaught and unstable distort, as they do also the rest of the Scriptures, to their own destruction.
17 You therefore, beloved, knowing this beforehand, be on your guard so that you are not carried away by the error of unprincipled men and fall from your own steadfastness,