That's one of the Keys (given to Peter) in understanding the scriptures...
And 2 Peter 3:15, 16 bear witness to this very thing. He states specifically that some things that Paul wrote were “hard to be understood”. Verse 15 is especially wonderful in this regard. “Paul..according TO THE WISDOM GIVEN UNTO HIM...” Peter wasn’t just discussing Paul’s difficulty in making himself clesr: he was discussing Paul’s epistles and WHY some people could not understand and wrested with the scriptures.