What is the significance of Jesus' spitting on the ground in the book of John?

Spittle in the time of Christ was considered a thing which expressed humanity at a most basic level. To use spittle to anoint his eyes shows that Christ had compassion at a very deep level.

As far as the Southern Baptist idea and I believe most Protestant faiths go, we believe that every action Jesus took him and everything he said has some sort of kingdom meaning. As far as the Scripture which is quoted I will give you how some of us Protestants will interpret that Scripture.

The ground is used by Jesus to signify that man was made from the dust of the Earth. The spittle is that Jesus must make the dust into a healing just as it was God who had to form man from the dust. The washing signifies two things, the first is that that dust is only a temporary thing, and must be cleansed, otherwise the man would still not be able to see. And the second is that if we are to see clearly we must be thoroughly cleansed.

The eternal significance of that is in the fact that in order to enter into the Kingdom of God we must cleanse the human part of our existence, and assume a Spiritual identity.

Hope this helps.

There are two instances in which the gospels tell of Jesus using spit in the eyes of a blind man whom he healed:

Mark 8:23-25: "When they arrived at Bethsaida, they brought to him a blind man and begged him to touch him. He took the blind man by the hand and led him outside the village. Putting spittle on his eyes he laid his hands on him and asked, "Do you see anything?" Looking up he replied, "I see people looking like trees and walking." Then he laid hands on his eyes a second time and he saw clearly; his sight was restored and he could see everything distinctly.

In this instance, Jesus was only partly successful at his first attempt, but succeeded on the second.

John 9:6-7 "When he had said this, he spat on the ground and made clay with the saliva, and smeared the clay on his eyes, and said to him, Go wash in the Pool of Siloam. So he went and washed, and came back able to see."

Saliva was widely reported to have medicinal properties in the ancient world. For example, Celsus and Galen mention its healing properties and Pliny collected together many instances of its use in the treatment of boils, pains, sores, snake bites, epilepsy and eye disease. Plinio Prioreschi reports in A History of Medicine: Roman medicine, page 728, that the god told Vespasian to spit in the eyes of a blind man, who would thereby be cured.

The Jews of the second temple period knew of a tradition that the saliva of a legitimate, first born heir would have healing properties against injury or disease. When we look back just a few verses in the context of John 9:6-7, at John 8:8, we read of Jesus proclaiming to be the son of God:

I testify on my behalf and so does the Father who sent me." So they said to him, "Where is your father?" Jesus answered, "You know neither me nor my Father. If you knew me, you would know my Father also."

Then in 8:25-29 (with further references by Jesus to God as his father, throughout the remainder of chapter 8):

So they said to him, "Who are you?" Jesus said to them, "What I told you from the beginning. I have much to say about you in condemnation. But the one who sent me is true, and what I heard from him I tell the world." They did not realize that he was speaking to them of the Father. So Jesus said (to them), "When you lift up the Son of Man, then you will realize that I AM, and that I do nothing on my own, but I say only what the Father taught me. The one who sent me is with me. He has not left me alone, because I always do what is pleasing to him."

Having told the Pharisees that he was the legitimate son of God, all that remained was for him to demonstrate this by performing something that first-century Jews expected a legitimate, first born heir to do. So, then in verse 9:1: "As he passed by he saw a man blind from birth."

Thus, the significance of Jesus using spit, in the context of John chapters 8 and 9, is the affirmation that he is the only begotten son of God.

Many people have the mistaken idea that Jesus came to do away with the Old Testament Laws, and that’s why the priests and Pharisees were so angry with Him. But Jesus had only good things to say about the Old Testament Law, Psalms and prophets. [Luke 24:44-45][John 5:39]

Jesus did not come to destroy the Law or the prophets; He came to fulfill. [Matthew 5:17, 18]

What He did speak out against was the Rabbinical writings that took the original 10 commandments and expanded them to include tons of minute laws to heap on men’s shoulders: [Matthew 23:1-4 KJV]

They also invented legal tricks to get around the laws themselves. [Mark 7:6-13 KJV]

The people in Jesus’ day knew all about all the Sabbath rules and other laws, that’s why the gospel writers didn’t think that it was necessary to define each one.

For instance, when Jesus spat in the dirt and made clay to rub on the blind man’s eyes to heal him on the Sabbath day, most people just think, “Yuck, what a mess!” But Jesus was making a clear statement to the scribes and Pharisees. The Pharisees had twisted the commandments so much that they became a burden to men instead of the blessing that was intended by God. The Pharisees say that you can’t make clay on the Sabbath day, because that would be considered work. So, on the Sabbath, if he had to spit, he would wait until he came to a rock, a tree or a wall, he would not spit on the dirt because he might make clay and defile the Sabbath. The scribes and Pharisees were so mad at Jesus for making clay on the Sabbath day that they didn’t even care that He had healed a man who had been blind from birth. (Avoiding spitting to make clay on the Sabbath was one of the Pharisee's traditions, not God's commandment.) Jesus did many other things on the sabbath to show where the Pharisees had gone wrong (like allowing the disciples to pick a few grains of wheat to snack on as they walked through a field [Luke 6:1-5]). Jesus said about the traditions of men:

Jesus said unto them, Full well ye reject the commandment of God, that ye may keep your own tradition. [Mark 7:9]

I will represent the Roman Catholic position on the verse.

Historically, St. Thomas Aquinas noted that this verse provided an example of Jesus' healing of sin. He cites St. Augustine for the interpretation that the blind man represents the human race. Sin is the spiritual blindness. When Jesus heals the blind man and allows him to see the light, he literally sees, which can be taken as a sign that he sees the error of his ways and wants to correct them by following the ways of God.¹

Additionally, St. Augustine, the early church father, wrote that the clay represented the anointing, and the blind man represented the catechumen, because he was anointed but not yet washed. So, I wouldn't really say that it's washing off the anointment, because it may be the effect of the anointment that healed the blindness or sinfulness. The washing is to emphasize that the blind man is no longer a catechumen, or that he is a baptized believer.² Meanwhile, the physical clay-and-spit is washed off, probably because that would be an eye irritant.

Source:

1. http://dhspriory.org/thomas/John9.htm

2. http://www.newadvent.org/fathers/1701044.htm