“Those who are healthy don’t need a physician ..." (Mark 2:17)

“Those who are healthy don’t need a physician, but those who are sick do: I didn’t come to call the devoted – but to call sinners to change their heart.” (Mark 2:17)
Here is the situation and question that prompted Jesus' statement:
Then he set off again along the seashore; and large crowds came to him and he taught them. Later as he was traveling, he saw Levi the son of Alphaeus sitting at the taxation booth, and said to him, “Follow me.” And he got up and followed him. Then later Jesus sat down to dinner at his house – and many tax collectors and sinners sat together with Jesus and his disciples: Because there were many who followed him. When the scribes and Pharisees saw him dining with tax collectors and sinners, they asked his disciples, “How is it that he eats and drinks with tax collectors and sinners?” (Mark 2:13-16)

Jesus was on a mission

What was that mission? Was it to be a sacrificial lamb? To die on the cross to cleanse the sins of humanity?

Nope. Sorry, but we must each suffer the consequences of our sinful activities - our self-centered actions.

Unless a person heeds the request of Jesus, just as he requested of the Levi: "Follow me."

And what does "follow me" mean?

Is Jesus asking the man to physically follow him - to walk behind Jesus where ever he goes? Certainly not. The Greek word translated to "follow" - ἀκολουθέω (akoloutheō) - means "let oneself be led by" or "to follow the thread of a discourse." This relates to following Jesus' teachings.

This is illustrated by the statement in Mark 2:13:
... large crowds came to him and he taught them.
So we must ask: if the purpose of Jesus' life was to die for the sins of humanity - then why did he bother teaching to people? Why did he walk from town to town in the hot desert-like temperatures of Judea and teach people in temples, courtyards and hillsides? Why did he make many disciples and students (at least 70 according to Luke 10:1) and ask them to go out and preach? Why didn't he just come and die on the cross?

Because dying for the sins of humanity - like some kind of sacrificial lamb - was not the purpose of Jesus' life.

And besides, the Supreme Being doesn't need a sacrificial lamb in order to forgive sins. He can forgive sins with a simple thought. This is evidenced by Jesus' recommending his students pray to God to forgive their sins (offenses):
Please forgive our offenses, as we forgive those who offend us. (Matt. 6:12)
Now there are many ecclesiastical institutions and their teachers who teach the sacrificial lamb concept. But as evidenced by the millions of prisoners jailed as a consequence for their (sinful) crimes, and the many other consequences that result from our own activities (good and bad) - Jesus' persecution on the cross did not remove this system of consequences, as it is part of our learning process.

This is illustrated by Jesus' use of the word "sinners" - translated from the Greek word ἁμαρτωλός (hamartōlos) - which means "specifically of men stained with certain definite vices or crimes" according to the lexicon.

What is a vice

It is an activity meant to please oneself - a self-centered activity.

Jesus' persecution was not some sort of ransom that removes the system of consequences for self-centered activities. If it were, he wouldn't have taught:
"Yet I say to you that anyone who becomes angry with his brother shall be subject to consequences, and whoever calls his brother ‘stupid’ shall be subject to judgment, and whoever speaks godlessness shall be subject to the fires of wickedness." (Matt. 5:22)
Jesus recognized and taught the law of consequences because this is the design of the physical world - in order to learn, there are consequences to self-centered activities that help others or hurt others - whether physically or emotionally.

However, Jesus' life and the manner of his leaving his physical body certainly have the potential to purify one's consciousness. But only if we hear and follow Jesus' teachings - and come to understand the reason Jesus allowed his physical body to be persecuted.

And following Jesus' teachings has the power to purify our consciousness. This is why Jesus is stating:
"Those who are healthy don’t need a physician, but those who are sick do."
The "sickness" that Jesus is speaking of relates to consciousness. It is the consciousness of self-centeredness. It is the notion that I am the most important person in my life.

In this state, our consciousness is polluted. Why?

Because first of all, we are not these physical bodies. I am not my body and you are not your body. Each of us is a spirit-person driving the physical body - much as a person gets into an automobile and drives it.

Jesus clarified this in his teachings:
“For this reason I say to you, don’t be anxious about your life, as to what you will eat or what you will drink; nor for your body and what you will wear. Is not the soul more than food, and the body more than clothing?" (Matt. 6:25)
"And don’t fear those who can kill the body but are unable to kill the self. Rather, fear those who are able to ruin both the soul and the body in hell." (Matt. 10:28)
What is the soul? The soul is each of us. It is not like an organ or something - as many have imagined it. We are each souls - spirit-persons occupying temporary physical bodies.

Secondly, each of us was created by the Supreme Being to exchange a unique loving service relationship with Him. We are each one of the Supreme Being's loving servants and playmates.

This means we were created to love and serve the Supreme Being - but with the freedom to love and serve Him or not. This is also clarified by Jesus in his teachings:

"For whoever does what pleases my LORD in the spiritual realm is my brother, sister and mother.” (Matt. 12:50)

And Jesus also practiced this:
Jesus also taught the process of coming closer to the Supreme Being - through prayer and glorification of God's Holy Names as he suggested one pray and connect with the Supreme Being:
" “Our spiritual LORD, Holy is Your Name. Show us Your sanctuary. May Your will be done on earth as it is in the spiritual realm." (Matt. 6:9-10)
To hallow someone's name means to glorify their name. It means to praise them and glorify them. Jesus is teaching his students to praise and glorify the Supreme Being's Holy Names.

Jesus' students and disciples also followed this instruction:
Then they all remained at the Temple, glorifying God. (Luke 24:52-53)
What does this mean, 'glorifying God'? It means the incantation of God's Holy Names. We find this was a critical teaching passed down through the ages by the prophets, from Abraham to David and others. The incantation of God's Holy Names - praising God's Holy Names in song or meditative repetition - is the process of worshiping the Supreme Being as revered by the prophets and taught by Jesus.

Why, one might ask, don't the ecclesiastical institutions that supposedly follow Jesus do this today?

Because they are not following Jesus. Sure, they might praise and glorify Jesus - and nothing wrong with this - but they are not following Jesus' teachings. This is why Jesus taught:
"Not everyone who says to me, ‘lord, lord,’ shall enter the sanctuary of the spiritual realm – only one who does what pleases my LORD in the spiritual realm. Many will say to me at that time, ‘Master, did we not prophesy in your name and in your name cast out demons, and in your name perform many miracles? And I will say to them, ‘I never knew you: Get away from me, you who practice wickedness.’" (Matt. 7:21-22)
Being the "only one who does what pleases my LORD" means to care for the Supreme Being and do what He wants us to do. This is the sum and substance of Jesus' teachings: