Hebrews 6:4-8
[These are people] who were once enlightened [by the Gospel message], who had experienced the gift from heaven [i.e., forgiveness, never ending life, etc. See Rom. 6:23], who had partaken of the Holy Spirit [See Acts 2:38],
2 Peter 1:9
But, anyone who lacks these qualities is [spiritually] blind and shortsighted, and has forgotten that he has been cleansed [i.e., forgiven] of his past sins.
2 Peter 2:20-22
For if people who have escaped from the defiling practices of the world by coming to know our Lord and Savior Jesus Christ, become tangled up in them again, and are overcome by them, these people are worse off than before they were converted.