No one who has been made holy can become lost. And the context of Hebrews 10:26-29 supports that view.
1) "Knowledge of the truth" refers to hearing and understanding the gospel,
not being chosen and transferred spiritually into Christ where individuals are "made holy" by the washing of regeneration.
2) No additional "sacrifice for sins" is available for those who did not fully embrace the gospel message.
3) Those that reject the gospel face judgement and the lake of fire.
4) To reject the gospel is to "trample on the Son and God.
5) As I have stated rather than suggested or implied or otherwise pussy-footed my words, the Greek word translated "sanctified" means, in this context, "set apart" under the New Covenant in His blood, and does not suggest he or she was set apart in Christ or made holy by the washing of regeneration. Christ laid down His life as a ransom for all, thus He bought those never to be saved, and His purchase set apart all humanity under the New Covenant in His blood.
6) I am saying that the people in view in
Hebrews 10:26-29 were
NEVER SAVED.