In 2 Peter 3:15-16, what does Peter say about some parts of Paul's letters?

Answer: They are hard to understand

Peter calls Paul 'our beloved brother' and says some parts of his letters are hard to understand, which ignorant and unstable people distort.

“He writes this way in all his letters, speaking in them about such matters. Some parts of his letters are hard to understand, which ignorant and unstable people distort, as they do the rest of the Scriptures, to their own destruction.”— 2 Peter 3:16 (BSB)