The following by Louis T. Talbot is from his book Bible Questions Explained --—
In these words the Holy Spirit refers to Hebrews, many of whom were INTELLECTUALLY convinced that Jesus was the Messiah. But because of bitter persecution, they were going away from the light they had, returning to Judaism.
Four things are said of the privileges these Hebrews were rejecting.
1. They WERE “ENLIGHTENED.” So also is every man who hears the Gospel, whether he accepts Christ or not. These were enlightened, but not born again.
2. They had “TASTED OF THE HEAVENLY GIFT.” Now it is one thing to taste; it is another thing to eat. Christ Himself is the Heavenly Gift. How many sinners have been under conviction, have admired the beautiful life of our Lord, have acknowledged that he died for a lost world, have even admitted that they expect one day to accept Him as a personal Saviour, and yet have refused to open their hearts to Him. They are among those who have only “tasted of the heavenly gift.”
3. They had been made “PARTAKERS OF THE HOLY GHOST.” Now the word “partakers” in the Greek means those who had been “going along with” the Holy Spirit, “in company with” Him. Every Jew who witnessed the descent of the Holy Spirit on the Day of Pentecost and heard Peter’s sermon, as recorded in the second chapter of Acts, was “in company with” the Holy Spirit. But, you will remember, the record tells us that some mocked and said, “These men are full of new wine” (Ac 2:13). To witness the power of the Holy Spirit is one thing; to be baptized by the Holy Spirit is another.
4. They had “TASTED THE GOOD WORD OF GOD, AND THE POWER OF THE WORLD TO COME”; that is, they had heard the Word of God, and had seen the dead raised, the leper cleansed, the eyes of the blind opened--—enough to convince them that Jesus was their Messiah and Lord.
Concerning these the Holy Spirit says: “It is impossible ... if they shall fall away, to renew them again unto repentance.” If they deliberately refuse to accept Christ as the only One who can save them, then they are doing the very same thing their fathers did; for they “crucify to themselves the Son of God afresh, and put him to an open shame.”
Moreover, if this passage of Scripture was written concerning Christians, it is very discouraging to those who hold “the falling away” doctrine; for they say a man can be saved, “fall away” or be lost, and then be converted again; whereas this passage from the Word of God says, “It is IMPOSSIBLE ... if they shall fall away, to renew them again unto repentance.”
Do you not see the fallacy of this doctrine, my friend? This one passage alone contradicts it definitely and finally.
But please note further the illustration given by the Holy Spirit in the verses which follow; it bears out the fact that verses 4-6 were written concerning those who had been “enlightened,” but not regenerated. In other words, the saved man “bringeth forth” fruit; but the man who rejects the Heavenly Gift bears “thorns and briers.” We are not saved by our good works; but we are saved unto good works. And “by their fruits ye shall know them.”
Yet another convincing proof of the fact that verses 4-6 describe the enlightened, but unregenerate, is seen in verse nine and the following verses. Here the Holy Spirit turns, as it were, from a description of those who had rejected Christ, and addresses the truly born-again Hebrew Christians. He calls them “beloved.” And He says, “But, beloved, we are persuaded better things of you”--—He had referred to the unregenerated as “those” (verse 4). Of “you,” “beloved” of God, “we are persuaded better things” than merely an intellectual knowledge. “We are persuaded ... things that accompany salvation.” These words unmistakably prove that, in the preceding verses, the born again souls were not in view at all.
And in verses 13-20, which follow, we find one of the strongest passages bearing upon the eternal security of the believer to be found in all the Word of God. The illustration is given of Jehovah’s promise to Abraham, at which time God confirmed His Word by His oath. According to the law of Moses, two or three witnesses were required to establish a fact in point of law. And here we read that by God’s Word and God’s oath--—by these two “immutable,” unchangeable things, we have a hope, “an anchor of the soul, both sure and stedfast.” What could be more plain, more reassuring, my friend? God’s Word is unchanging; His promise is sure! (Louis T. Talbot, Bible Questions Explained, pp. 112-114)
Things Hard To Be Understood: David Cloud