The Bible is very plain in declaring that all face the consequences of sin, which is death:

Romans 5:12 – “…death came to all men, because all have sinned.” (NIV)
Romans 6:23 – “For the wages of sin is death: but the gift of God is eternal life through Christ Jesus our Lord.”
Romans 3:10/ Psalm 14:3/ Psalm 53:3 – “There is none righteous, no, not one.”

And the Apostle James showed that every sin is the same in regard to its penalty in James 2:10 – “For whosoever shall keep the whole law, and yet offend in one point, he is guilty of all.”

But Jesus came and gave his life as a ransom for all (1 Timothy 2:5-6). Because Jesus paid a corresponding price for Adam, all people will be released from death “in due time.” Those who can accept Christ in this age are called to consecrate or dedicate their lives to him now in order that they can live and reign with him in the next age.

Romans 6:23 (above) is verified by 1 Corinthians 15:22, “For as in Adam all die, even so in Christ shall all be made alive.” 

and Romans 8:1,2, “There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.  For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.”

That the Apostle John in 1 John 5:17 says, “…there is sin that does not lead to death,” (NIV), indicates that this must be something other than the Adamic death.  We read in Jude 12, referring to false teachers who had slipped into the early church, “These men are…shepherds who feed only themselves. They are clouds without rain, blown along by the wind; autumn trees, without fruit and uprooted — twice dead.” (NIV)

In 2 Peter 2, the Apostle Peter writes about false prophets and teachers. He uses many of the same descriptive terms as Jude. In verse 10 he writes, “This is especially true of those who follow the corrupt desire of the sinful nature and despise authority…”  In verses 20 and 21, he sums up their fate:  “If they have escaped the corruption of the world by knowing our Lord and Savior Jesus Christ and are again entangled in it and overcome, they are worse off at the end than they were at the beginning.  It would have been better for them not to have known the way of righteousness, than to have known it and then to turn their backs on the sacred command that was passed on to them.”  

In other words, these were Christians who had accepted Christ’s deliverance but then completely returned to sinful practices.  If a Christian who has been bought from the curse of sin and death deliberately turns away from God and from his Savior and goes back into a life of utterly willful sin (not just sins of weakness, with which we all commit), then he is treating “as an unholy thing the blood of the covenant that sanctified him” (Hebrews 10:29 NIV) and there is “no sacrifice for sins” left  (Hebrews 10:26  NIV).  Having renounced the deliverance from the first (Adamic) death, that person would die a “second” death, from which there is no redemption, hence no resurrection.

Additional Resource:
Christian Questions Podcast 
Episode #1265: “What Sins Can Never Be Forgiven?”
Identifying what unforgivable sins are and their consequences
Preview Video
CQ Rewind Show Notes