Jesus is saying that to willfully and verbally deny Him before men is the UnpardonableSin.  <p>Why is believing on Jesus and confessing Him before men so important? -> Because Jesus is `God`.  <br>No one can be accepted by `God` who has rejected Him.<p>Jesus states that a person`s words against Him requires Him to speak against them to His HolySpiritFather. <br>What does that mean? -> It means that His HolySpirit will not dispense Grace to the denier and so leave them to inevitable destruction.<p>If Jesus is not a person`s advocate before His HolySpirit they are condemned to the LakeOfFire Mat 12:32.<p>Faithfulness is a characteristic of our LordJesusChrist. If faithfulness is not a part of a person`s character they will deny Him eventually. <p>A person`s denial of Him will require His denial of them. <p>See DenyingJesus  for clarity on how unbelievers of different levels DenyJesus.