"I tell you the truth, whoever hears my word and believes Him who sent me has eternal life and will not be condemned; he has crossed over from death to life." (John 5:24)

Here Jesus is very clear about what his mission is, and what it means to be a follower of Jesus.

The key phrase here is: 
"...whoever hears my word and believes Him who sent me..." 
There are two elements here:

The fist is hearing Jesus' "word." What is Jesus' "word?"

"Word" is translated from the Greek word λόγος (logos), which means "teaching" or "doctrine."

Thus, Jesus is speaking of hearing his teachings: His instructions and his message.

The second is "believes Him who sent me." Who is the "Him" here? Who sent Jesus? We know that it isn't Jesus, because Jesus is distinguishing between himself and the "Him" who sent him because there are two subjects here: "Him" and "me".

So Jesus is talking about someone else sending him. Who might that be?

Jesus is speaking of the Supreme Being. The Supreme Being sent Jesus.

The word "believes" here is translated from the Greek word πιστεύω (pisteuō), which means "to have confidence" and "to entrust" and "to be instrusted." Thus the word relates to trust rather than simply belief.

Certainly to believe in God's existence is no big thing. Even the Jewish Pharisees who were offensive against Jesus and God believed in God's existence.

Rather, it is trusting in God that Jesus is speaking of. It is taking shelter in the Supreme Being. It is giving ones heart to God that Jesus speaks of.

These actions lead one to "eternal life" - translated from the Greek phrase, ζωὴν αἰώνιον. The word ζωὴν means "life" but more specifically relates to the "living soul" according to the lexicon. Further, it relates to "the absolute fullness of life."

The word αἰώνιον means, according to the lexicon, "without beginning and end" "that which always has been and always will be" and "without end, never to cease, everlasting."

Why is this important? Currently we are dwelling within temporary physical bodies which will get sick and die within a few years. These bodies are definitely not eternal. And our lives that are currently focused upon these temporary physical bodies, and the temporary forms and things of the physical world are also not eternal. We are thus currently living non-eternal lives focused upon things that will decompose.

Jesus also explained this state of existence when he told one of his students:
“Follow me, and let the dead bury their own dead.” (Matt. 8:22)
In other words, we might consider ourselves alive as we live our day-to-day physical lives, focused upon making money, taking care of family and other survival-oriented activities. But by themselves these activities, according to Jesus' definition, are dead. They are focused upon the decomposing matter of a temporary physical world - a world of illusion and mirage.

Yes, illusion and mirage. Consider for example a person who is walking through the desert and thinks he sees a pond of water. He dives into the supposed pond only to get a mouthful of sand. The water was an illusion.

In the same way, we are walking through this physical world within a physical body thinking there is happiness here in the material things of the world - whether it be wealth, fame or a big family and a big house. But these only offer the illusion of happiness. We dive into these things as the thirsty man in the desert thought he was diving into the pond. Just as the thirsty man ended up with only a mouthful of sand, we end up with only emptiness from our supposed gains within the physical world.

Yes, we find that money brings no happiness - only anxieties and turmoil as we struggle to get it, then seek to protect it, and lament when we lose it.

And we find that fame and popularity bring no happiness - only emptiness as those who are famous struggle to please fans and find many are simply envious and seek their own fame.

Even family life - which sometimes gives us a glimpse of real love and kindness - still results in many struggles, as family members fight and become hostile at times, and then in the end, family members simply die and leave the rest of the family behind. Gradually, everyone in the family dies - leaving behind only the younger offspring, who follow in their parents' footsteps and die to leave their own children behind.

Thus we find one of the emptiest occasions in family life is when a family member dies. We thought they'd be with us forever, but they weren't. They left us.

All of this is emptiness. Whether it is fame, fortune or family, it is empty. It has no life. And it has no eternality.

Jesus is offering his students eternal life. He is offering them a relationship with the Supreme Being. He is stating that if they trust in God - giving their hearts to the Supreme Being - and they follow Jesus' instructions - they will have eternal life.

This eternal life comes in the form of a loving service relationship with the Supreme Being. This is eternal because the Supreme Being is eternal, and our spiritual forms - not these physical bodies - are also eternal, and thus get to exchange a loving service relationship with God that does not end.

Jesus confirmed this with his most important instruction:
“ ‘Love the Lord your God with all your heart and with all your soul and with all your mind.' This is the first and greatest commandment.” (Matt. 22:37-38)


(See also the Gospels of Jesus for the Book of John - translated from the original Greek texts without ecclesiastical sectarian influence.)