Jesus used parables to fulfill prophecy,
You said:
it is true some of the disciples did not understand at some point but note that after Jesus resurrection when the spirit was sent to all who believed, they understood, same today, people who received the Holy Spirit that jesus said he would send ""the comforter" understand, Peter was quite correct in saying that Paul's texts, far more complex in structure and vocabulary was difficult to understand for the common man. Still today we see very different interpretations to most of Paul's verses and concepts, definitely not easy to understand. so many denominations for so many different interpretations. For My part I rely fully on the words of Jesus and seldom quote Paul for clarity.
As for understanding Paul: The veil of Paul is easily lifted if:
#1. One reads Paul's words in light of the false heresy of Circumcision Salvationism for Initial Salvation in Acts 15 in the KJV.
#2. One understands that Paul was referring many times to Initial Salvation and that he was not teaching that we can later abide in sin with the thinking we are saved all because we have a belief alone in Jesus (i.e., Easy Believism). Yes, we are saved initially by faith (a belief alone) in Jesus, but that is not how the faith continues. The faith continues with Sanctification of the Holy Spirit to live a holy life pleasing to God.
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