'Letters' in the Bible

And be certain that the long waiting of the Lord is for salvation; even as our brother Paul has said in his letters to you, from the wisdom which was given to him;

And as he said in all his letters, which had to do with these things; in which are some hard sayings, so that, like the rest of the holy Writings, they are twisted by those who are uncertain and without knowledge, to the destruction of their souls.