Consider carefully what Jesus is saying. If we are these physical bodies, then killing the body should end our existence, right? But Jesus is clearly saying "after that can do no more." This means there is more. This means the body's death is not the end of our existence.
Jesus stated this fact - that we aren't the physical body - elsewhere as well. In fact, he made a similar statement in the Book of Matthew, but worded a little differently:
While some may contend that this is the same statement as Luke 12:4 but worded slightly differently, it matters not. What matters is that the Book of Matthew clarifies Jesus' statement in Luke 12:4. It states clearly that the soul lives on after the body dies."Do not be afraid of those who kill the body but cannot kill the soul." (Matt. 10:28)
Some have contended that the soul is but a part of the body - like some sort of moral "organ" or something. So they will indicate that their soul may become separated from them somehow.
This is incorrect. It is not that I have a soul: I am the soul.
The soul is the spirit-person who exists on a dimension unseen by the physical senses - a dimension aloof of the material dimension. The soul is the person - the personality - who is composed of spirit, not matter.
This is why so many of us have identity crises - typically as we age, and for some, with regard to their being heterosexual or homosexual, or even male or female (now called gender confusion). But these - along with the body's race, nationality, and so on - are all false identities, because we are falsely identifying with these physical bodies.
For example, consider your body when it was a baby. Do you have a picture of that body? If you do, you can see the body was very small, and doesn't look at all like the body you have now. Was that body you? And if so, why do you now identify with your current, much larger body? Did that baby body get stretched out or just expand into the "you" right now?
Certainly not. In fact, every atom and molecule that made up that baby body is now somewhere else: They have all been excreted out of the body and replaced by new atoms and molecules. Scientists say the body recycles all of its atoms and molecules within at least five years.
Now since the baby body was made of different molecules, you have effectively changed bodies since then. You are wearing a completely different body.
So if you are the body, which body is you? The baby body or the adult body?
Neither. Since you are changing bodies, we can logically determine that we cannot be these bodies. Since we are the same person when our bodies are babies - or children - or teenagers - or young adults - then we must be something different than the body.
We are, in fact, composed of spirit. Certainly each of us has a personality, and that's why we are each unique and individual. But this unique, individual personality is not the physical body. We are each spirit-persons.
Jesus also taught this clearly:
"The spirit is willing, but the flesh is weak.” (Matt. 26:41 and Mark 14:38)
“Therefore I tell you, do not worry about your life, what you will eat or drink; or about your body, what you will wear. (Matt. 6:25 and Luke 12:22)
"The spirit gives life; the flesh counts for nothing. The words I have spoken to you—they are full of the spirit and life." (John 6:63)
In fact, Jesus also clearly identified himself as being spirit, and not the physical body:"Flesh gives birth to flesh, but the Spirit gives birth to spirit." (John 3:6)
Jesus called out with a loud voice, “Father, into your hands I commit my spirit.” When he had said this, he breathed his last. (Luke 23:46)And because Jesus taught his followers that they - and he - were spirit, not these physical bodies, they also identified Jesus as spirit and not his physical body:
When he had received the drink, Jesus said, “It is finished.” With that, he bowed his head and gave up his spirit. (John 19:30)
And when Jesus had cried out again in a loud voice, he gave up his spirit. (Matt. 27:41)These teachings, most certainly, cancel out so many of the doctrines proposed by ecclesiastical sectarian institutions and their teachers who suggest that our physical bodies will rise to heaven - some say, after dancing on the grave or waiting in purgatory and so on. These physical-body speculative teachings make no scientific sense, nor are they consistent with Jesus' teachings or the teachings of any of the prophets.
On a practical level, we can know this as well. When we see a person die, suddenly their body becomes lifeless. Yet the dead body is the same as the live body. There is no difference in tissues, organs or molecules. The only difference is that the personality and the force that drove the body is now gone. That living force is the spirit-person who drives the physical body.
The reality is that not only are we spirit in composition, but the Supreme Being is spirit in composition. Just consider Jesus' statement in this context:
When we identify ourselves as spirit and not these physical bodies, we can become freed from all of the identity crises and all of the racism and all of the hatred that comes from or is related to the fact that we are falsely identifying ourselves with these physical bodies."God is spirit, and his worshipers must worship in the spirit and in truth." (John 4:24)
And once a person realizes they are not the physical body, they can become freed from the problems of aging, sickness and death. Because the physical body is a vehicle or temporary possession of the spirit-person within, we can know that the physical body's disposition is not our concern.
Our concern is the condition of our spirit-person. Are we living the life that will nourish and sustain our spirit-person within?
Jesus stated the key to nourishing the spirit-person within:
“My food,” said Jesus, “is to do the will of Him who sent me and to finish His work." (John 4:34)Jesus is stating that what is nourishing to his spirit-person is to please the Supreme Being. The word θέλημα (thelēma) - translated to "the will" in the above statement by Jesus - actually means to do "what one wishes" or do do what pleases the person.
Jesus is seeking to please the Supreme Being and that is giving the spirit-person Lord Jesus the food - the nourishment - that he needs.
This - wanting to please God - is quite simply love. Why else would Jesus want to do what pleases the Supreme Being? Because Jesus is loving the Supreme Being.
And this is also what Jesus wanted his students - and all of us - to do as well, because this - and only this - will make us spirit-persons truly happy:
“ ‘Love the Lord your God with all your heart and with all your soul and with all your strength and with all your mind’" (Luke 10:27)