A.T. Robertson Commentary Hebrews 6:4

"For as touching those who were once enlightened and tasted of the heavenly gift, and were made partakers of the Holy Spirit," — Hebrews 6:4 (ASV)

As touching those who were once enlightened (τους απαξ φωτισθεντας). First aorist passive articular participle (the once for all enlightened) of φοτιζω, old and common verb (from φως) as in Lu 11:36. The metaphorical sense here (cf. John 1:9; Ephesians 1:18; Hebrews 10:32) occurs in Polybius and Epictetus. The accusative case is due to ανακαινιζειν in verse 6. Hαπαξ here is "once for all," not once upon a time (ποτε) and occurs again (9:7,26,27,28; 12:26,27).

Tasted of the heavenly gift (γευσαμενους της δωρεας της επουρανιου). First aorist middle participle of γευω, old verb once with accusative (verse 5, καλον ρημα, δυναμεις), usually with genitive (Hebrews 2:9) as here.

Partakers of the Holy Ghost (μετοχους πνευματος αγιου). See 3:14 for μετοχο. These are all given as actual spiritual experiences.

And then fell away (κα παραπεσοντας). No "then" here, though the second aorist (effective) active participle of παραπιπτω, old verb to fall beside (aside), means that. Only here in N.T. In Gal 5:4 we have της χαριτος εξεπεσατε (ye fell out of grace, to law, Paul means).