Hebrews 6:4
Impossible -- Note vs. 6, (Hebrews 6:6) this "impossibility" is "while" (or seeing) they crucify the Son of God afresh. The writer is saying that salvation is ONLY found in Christ, for the Hebrews to go back to the Law is to forfeit God’s salvation. There is NO WAY outside of Christ to be saved!
[Baptist say -- see The Arminian view has it if you loose your salvation you cannot get it back, according to this passage.]
Enlightened -- how?
Tasted -- As contrasted in Christ tasting the bitterness of death for every man -- Hebrews 2:9.
Heavenly gifts -- forgiveness of sins, salvation, Ephesians 2:8.
Partakers -- sharers
Holy Ghost -- spiritual gifts
Hebrew Writer is saying:
1. You can’t be renewed by the Jewish system
2. Can’t be renewed while they are re-crucifying Christ who is their only hope.