Once again I have to disagree with Paul.

Here is what Paul wrote in Hebrews (Hebrews is attributed to Pauline authorship but there is quite a bit of disagreement within the Christian world on that point). 

Hebrews 6:4-6(NKJV)

For it is impossible for those who were once enlightened, and have tasted the heavenly gift, and have become partakers of the Holy Spirit, 

and have tasted the good word of God and the powers of the age to come, 

if they fall away, to renew them again to repentance, since they crucify again for themselves the Son of God, and put Him to an open shame.

It seems to me that Paul is saying that if one falls away for a time and then wants to return to the family of God it will not be allowed.  In fact Paul says it is impossible for that to happen. 

Now let's compare that to what Jesus said. 

Matthew 12:31-32(NKJV)

“Therefore I say to you, every sin and blasphemy will be forgiven men, but the blasphemy against the Spirit will not be forgiven men. 

Anyone who speaks a word against the Son of Man, it will be forgiven him; but whoever speaks against the Holy Spirit, it will not be forgiven him, either in this age or in the age to come.

Who ya going to believe?  I will side with Jesus every time.

But let's go a little deeper.  Is Paul trying to purposely deceive?  I don't think so.  One of the things I have noticed in Paul's writings is that he is a bit like a little Jewish mother, he is really good at trying to lay guilt trips on people to manipulate them. 

This is purely speculation on my part but I think this is an emotional manipulation on Paul's part.    Paul seems to be saying how can you fall away after tasting all the goodness of being part of the family of God?  Don't expect to be welcomed back. 

But think it through.  That is an awfully unforgiving attitude isn't it?  In fact it is the opposite of Jesus' real message isn't it?  Jesus said "Anyone who speaks a word against the Son of Man, it will be forgiven him…..".  Jesus didn't put any time limit on it nor did Jesus say hey this is a onetime offer did he? 

To me this is another example of why we need discernment as we study God's Word.  Man adds and man subtracts from God's Word.  Almost always with good intentions.  I'm sure Paul had the very best of intentions in this case even though he directly contradicts Jesus. 

I caught our Pastor doing something like this in a class a couple of years ago.  He made a statement that while well intentioned simply wasn't Scripturally correct and I called him on it in front of the class.  When I explained the error he agreed and we moved on, no big deal.  It was funny though because for the rest of the night if he was getting ready to say something close to the edge he would glance over at me like he was thinking "oh crap is he going to correct me again?".  :)

So how do we discern which is which?  First and foremost rely on the Holy Spirit for guidance.  That is one of His primary purposes.  In addition try this Bible study rule that I use.  I am always looking for confirmation of a principal or belief in both the Old Testament and the New Testament.  And I always put the words of Jesus above all others!