4:14 Having then a great high priest, who has passed through the heavens,
Jesus, the Son of God, let us hold tightly to our confession.
 

4:15 For we don't have a high priest who can't be touched with the feeling of our infirmities,
but one who has been in all points tempted like we are, yet without sin.

4:16 Let us therefore draw near with boldness to the throne of grace,
that we may receive mercy, and may find grace for help in time of need.

5:1 For every high priest, being taken from among men,
is appointed for men in things pertaining to God, that he may offer both gifts and sacrifices for sins.

5:2 The high priest can deal gently with those who are ignorant and going astray,
because he himself is also surrounded with weakness.
5:3 Because of this, he must offer sacrifices for sins for the people, as well as for himself.
5:4 Nobody takes this honor on himself, but he is called by God, just like Aaron was.

5:5 So also Christ didn't glorify himself to be made a high priest, but it was he who said to him,
"You are my Son. Today I have become your father."
5:6 As he says also in another place, "You are a priest forever, After the order of Melchizedek."

5:7 He, in the days of his flesh,  having offered up prayers and petitions
with strong crying and tears to him who was able to save him from death,
and having been heard for his godly fear,
5:8 though he was a Son, yet learned obedience by the things which he suffered.
5:9 Having been made perfect, he became to all of those who obey him the author of eternal salvation,
5:10 named by God a high priest after the order of Melchizedek.

5:11 About him we have many words to say, and hard to interpret,
seeing you have become dull of hearing.
5:12 For when by reason of the time you ought to be teachers,
you again need to have someone teach you the rudiments of the first principles of the oracles of God.
You have come to need milk, and not solid food.
5:13 For everyone who lives on milk is not experienced in the word of righteousness,for he is a baby.
5:14 But solid food is for those who are full grown,
who by reason of use have their senses exercised to discern good and evil.
6:1 Therefore leaving the doctrine of the first principles of Christ,
let us press on to perfection--not laying again a foundation

• of repentance from dead works,
• of faith toward God,
• 6:2 of the teaching of baptisms,
• of laying on of hands,
• of resurrection of the dead,
• and of eternal judgment.

6:3 This will we do, if God permits.

6:4 For concerning those

• who were once enlightened
• and tasted of the heavenly gift,
• and were made partakers of the Holy Spirit,
• 6:5 and tasted the good word of God,
• and the powers of the age to come,

6:6 and then fell away, it is impossible to renew them again to repentance;
seeing they crucify the Son of God for themselves again, and put him to open shame.
 

6:7 For the land which has drunk the rain that comes often on it,
and brings forth a crop suitable for them for whose sake it is also tilled,
receives blessing from God;
6:8 but if it bears thorns and thistles,
it is rejected and near being cursed, whose end is to be burned.

6:9 But, beloved, we are persuaded of better things for you,
and things that accompany salvation, even though we speak like this.
 

6:10 For God is not unrighteous, so as to forget your work and the labor of love
which you showed toward his name, in that you served the saints, and still do serve them.

6:11 We desire that each one of you may show the same diligence
to the fullness of hope even to the end,
6:12 that you won't be sluggish,
but imitators of those who through faith and patience inherited the promises.

What does it mean by "falling away" here? It means to recrucify Christ after having followed Christ, having been enlightened and given sufficient evidence of the truth of His Word. It is a rejection of Christ himself, as the Jews had rejected him at calvary.

Does this section mean a Christian could lose his salvation? Although that is a possible interpretation if one reads just this section alone, it seems inconsistent with overs verses. 1John 2:19, for example, indicates that true believers do not even "fall away". However, there are also many verses that indicate that not everyone who calls themself a "Christian" actually is a believer (Matt 7:21). And if one is a real believer, then there should be some inevitable "fruit" as external evidence of their belief (Matt 7:19-20). Heb 6:7,8 indicates that this person is not such a believer, but merely a nominal Christian.

The situation described in this section may be likened to the time when Israel came out of Egypt, through the desert to the Jordan River, and despite all that they experienced of God's power, they refused to enter the promise land. So God sent them back into the desert to die.

This section describes a person who has been enlightened to understand the gospel. But understanding it doesn't make one saved. They have had a taste of the heavenly gift, possibly referring to the Holy Spirit which Peter calls a gift in Acts 2:38. In which case, "tasted" and "shared in" both refer to their experience with the Holy Spirit. The greek word for "shared in" (metochos) is literally "became partners with". It is first used in the New Testament in Lu 5:7 "And they beckoned unto their partners, which were in the other ship, that they should come and help them. And they came, and filled both the ships, so that they began to sink." This is the type of relationship that the Holy Spirit has with those He is helping to come to Christ. Such people do have an experience with the Holy Spirit even though they don't have the permanent indwelling of the Holy Spirit promises to believers as in Eph 1:13,14 "In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise, Which is the earnest of our inheritance until the redemption of the purchased possession, unto the praise of his glory."

They also experienced how good the Word of God is, although had yet to really put their faith in it. They also experience miracles, which made them even more accountable in God's sight just as Jesus had said: "Woe unto thee, Chorazin! woe unto thee, Bethsaida! for if the mighty works, which were done in you, had been done in Tyre and Sidon, they would have repented long ago in sackcloth and ashes. But I say unto you, It shall be more tolerable for Tyre and Sidon at the day of judgment, than for you." Matt 11:21,22

A person who has such knowledge and experience, and rejects Christ will be permanently lost. Having reject what the Holy Spirit had been revealing to him, he has sinned against the Holy Spirit, and as Jesus says, "But he that shall blaspheme against the Holy Ghost hath never forgiveness, but is in danger of eternal damnation." Mr 3:29 Having led the person to the point of salvation, having given him sufficient evidence to make a decision, and having been rejected, the Holy Spirit breaks His partnership with the unbeliever and never returns. For "But that which beareth thorns and briers is rejected, and is nigh unto cursing; whose end is to be burned."Heb 6:8

Heb 6:4 It is impossible for those who have once been enlightened, who have tasted the heavenly gift, who have shared in the Holy Spirit, (NIV)

Heb 6:4 For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, (AV)

We must be careful to note that the Greek word translated "partakers" does not mean "possessors," in the sense that these Hebrews possessed the Holy Spirit as an indwelling Person who had come to take up His permanent abode in their hearts. The word is a compound of the Greek verb "to have or hold", and a preposition meaning "with" thus "to hold with." It is used in Luke 5:7 where it is translated "partners," signifying one who co-operates with another in a common task or undertaking. It is used in Hebrews 1:9 where the angels are "fellows" of our Lord, partners or associates with Him in the work of salvation. It is used in Hebrews 3:1 where the recipients of this letter are called participators in the heavenly calling. That is, they participated together in the heavenly calling. These Hebrews had left the earthly calling of the nation Israel, and had identified themselves with the Church which has a heavenly calling. It is used in Hebrews 3:14, where it speaks of those who participate together in the Lord Jesus.

The word (metochos) was so used in secular Greek. Moulton and Milligan give examples of its usage in the following phrases: "We, Dionysius son of Socrates and the associate collectors;" Pikos son of Pamonthes and his colleagues," "the Joint-owner of a holding," "I am unable to take part in the cultivation," "Some do so because they are partners in their misdeeds." Thus the word signifies one who participates with another in a common activity or possession. It is so used here. These Hebrews became participators in the Holy Spirit insofar as an unsaved person can do so, namely, in the sense that they willingly co-operated with Him in receiving His pre-salvation ministry, that of leading them on step by step toward the act of faith. He had led them into the act of repentance. The next step would be that of faith. Here they were in danger of turning their backs upon the Spirit and returning to the sacrifices. Peter in his first epistle (1:2) in the words, "through sanctification of the Spirit unto obedience," speaks of this work of the Holy Spirit on the unsaved, setting them apart from unbelief to faith. This word in its context does not at all imply that these Hebrews had been born of the Spirit, sealed with the Spirit, indwelt by the Spirit, anointed with the Spirit, baptized by the Spirit into the Body of Christ, or filled with the Spirit. This work of the Holy Spirit in leading them on towards faith was a once-for-all work, so thoroughy done that it needed never to be repeated. However, there was nothing permanent of itself in this work, for the work was only a means to an end. This is shown by the aorist participle used, referring to the mere fact, not a perfect, speaking of a finished act having present results. The fact that the writer did not use the perfect tense here, which is a specialized tense, but rather the aorist, which is the maid of all work, points to the incompleteness of the work of the Spirit in the case of these Hebrews. So far as the work had been done, it was perfect, thorough. But it would not be complete until the Hebrews accepted the proffered faith from the Spirit. The incompleteness of the work would be due, therefore, not to the Spirit, but to their willingness to go on as a partner or cooperator with the Spirit.

See also More Discussion over the Interpretation of Hebrews 6:4-8.