The writer here reminds us that what he is writing is by inspiration of God. All Scripture is given by inspiration of God. None of the writers sat down with pen and “paper” and wrote what they felt like writing. They wrote under God’s direction and because they were all holy men, they obeyed what they were told to do.
The Bible is not a book of suggestions. It is not one of many sources of truth. The Bible is God’s direct communication with man. It is a one sided communication because God is always right and we always need to be guided in the right way. Those who choose to ignore or reject God’s Word suffer the consequences of that disastrous choice, both now and for all eternity. At some point every person alive has ignored and even rejected God’s Word. By God’s grace, some have realized the utter folly of such a choice and have repented toward God and trusted in the Lord Jesus Christ as Saviour.
In verse 4 we are reminded of the facts. It is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost . . . The devil loves to play with God’s Word and he loves to twist and contort it for his own wicked purposes. He twisted God’s Word in the Garden and Eve was deceived by his deception. Adam chose to believe the lie.
As we mentioned yesterday, we need to let God show us the right understanding on any doctrine that He gives us. It is abundantly clear from the Scriptures up to this point, that God’s salvation is a gift from Him. It is also abundantly clear that His gift is so precious that it never loses its value. Those who receive that Gift have It for all eternity. With that in mind, how then do we understand what God is telling us in these verses.
Verse 4 actually gives justification for God sending lost people to the lake of fire. In Romans 1:20 we read:

Romans 1:20 For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse:

Notice that God declared that the “invisible things of Him” . . . “are clearly seen”. No one will stand before God at the great white throne judgment and justly claim they did not know there was a God and of His greatness. There is a language that God uses to communicate with man that makes His existence irrefutable. That language is painted in the heavens. Psalm 19 tells us of that. There is no need for any translation of that language. Every nationality can look up into the same heavens and they can know there is a true God.
In verse 4 of our text God spoke of those who were once enlightened. Children are much more likely to accept the fact that there is a God. They are much more likely to accept that God made the things they see. The longer a person is brainwashed in the “educational/indoctrination” system of our world, the more likely they are to reject what they know to be true because adults have deceived them into believing the lies that they have developed. There are children that go to Sunday School and sit in church services and they talk about the things they have heard. They can be quite excited about those things, but as they hear lies from adults around them, they doubt that which God puts into their conscience. There are also adults in this same position. They are just like Adam and Eve. Adam and Eve had sharper minds and more keen consciences than anyone else every will have. Yet, Eve was deceived and Adam willingly chose to believe the lie that his wife gave him. If they could be convinced of a lie, why not those who are born as lost sinners and thus already corrupted in their thinking. The sin nature is powerful. It is not more powerful than the truth, but it is powerful.
God is showing us how powerful the Truth is. It will show a person the facts. Man is an emotional being and he can and does get excited about many things. Excitement does not equal salvation.
Another word the devil likes to distort is the word “tasted”. We all like to taste different things. From our childhood we develop a liking for certain tastes and we also dislike certain tastes. Something may taste good to you but another person will turn up their nose at it.
God gives the person the opportunity to taste of the heavenly gift. The person needs to decide what he or she will do with that taste. Will they spit it out or will they pursue more of that taste.
John 16:7-12 states:

John 16:7 Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you.
8 And when he is come, he will reprove the world of sin, and of righteousness, and of judgment:
9 Of sin, because they believe not on me;
10 Of righteousness, because I go to my Father, and ye see me no more;
11 Of judgment, because the prince of this world is judged.
12 I have yet many things to say unto you, but ye cannot bear them now.

The Holy Spirit is active in every person’s life. Every lost sinner is affected by the work of the Holy Spirit in their heart and life. We see evidence of this all around us. There are multitudes of people who refuse to go to a good church because they do not want to hear what God has to say. They already know they are sinning. They already know they are under God’s judgment. Look at the hatred expressed by the sodomite community. They hold their public parades but they do not even want the police to be involved in their marches. They know what they are doing is wrong but they are in open rebellion against God. That is just one example of many.
In verse 5 we are further warned of the fact that the ungodly have tasted the good Word of God. Again, there are people who get quite emotional when they hear the Word of God preached. There are people who will break down in tears when they hear the Word of God preached or when they read a certain passage. However, God says many of these people never go beyond feelings. Feelings do not save.
Lost people can observe the power of God’s salvation in a true saint. This is another reason why the New Evangelical crowd is so wrong. They teach that salvation is often indiscernible in the person’s life. They may still smoke and drink and swear, but they are saved because they said so, or they were led in a prayer. There are Hollywood actors who profess to be saved and still carry on in their sins. I read of a U.S. politician who was invited to speak at a “Christian” conference and he talked about God and how we need to get Him back in the centre of our lives. This man made reference to Augustine as the inspiration for getting back to God. Augustine was a Catholic monk who hated God. He developed the lie of purgatory. John Calvin was also heavily influenced by Augustine.
This same politician who spoke of the importance of building our lives on God, also sits on one of the U.S. house committees. He was questioning a person and had no problem swearing in his questions to this person. The world gets all excited about that brand of “christianity”. It is nothing and the devil is quite content with that kind of a presentation. If he can keep people in the dark, that is all he wants.
In verse 6 God speaks of this person falling away. They saw the power of God, they experienced the excitement of the truth, but they never accepted it for themselves. They were being moved by the convicting work of the Holy Spirit but they stubbornly and foolishly walked away from it.
God declared that it is impossible for such a person to turn to God in repentance. Why is that? They crucify to themselves the Son of God afresh. That is what the Catholics do every time they have the “mass”. That is what many others do as well.
What God is addressing here is those who reject Jesus Christ as the Son of God. Jesus Christ was crucified in large part because He declared Himself to be the Son of God. The Jews accused Him of blasphemy for making Himself equal to God the Father. He did not make Himself equal to His Father. He was and is equal to His Father. The unbelieving masses rejected that fact and they cried out for His crucifixion.
The people described in our text are doing the same thing. They reject Jesus Christ as the Son of God. They may make that statement with their mouth, but their heart is far from agreement with the true Son of God. Thus they crucify to themselves the Son of God afresh. They put Him to open shame. Jesus cannot be crucified again. He died once for our sins. He was buried and He rose again. He is seated on the right hand of His Father in glory ever since His ascension. He is coming back in power next time.
Those who reject His Work doom themselves. There is no salvation outside of trusting in the true God and the Lord Jesus Christ, Who is the Son of God. If a person does not want to receive that God and Saviour, there is no hope. If a person wants to insist on their corrupted brand of god and saviour, they have no hope. They condemn themselves.

John 3:19 And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil.