Right before his crucifixion, Jesus was made to carry his cross and to wear a crown of thorns. Why was he made to wear the crown of thorns?
As Ray asserted, the crown was mockingly placed on Him because Jesus was charged with the crime of being "the King of the Jews", while the Jews already had a king, at least according to the Romans.
There is, however, an important symbolism that is also present in this.
In Genesis 3, thorns and thistles are part of the curse of the first sin.
And to Adam he said, “Because you have listened to the voice of your wife and have eaten of the tree of which I commanded you, ‘You shall not eat of it,’ cursed is the ground because of you; in pain you shall eat of it all the days of your life; 18 thorns and thistles it shall bring forth for you; and you shall eat the plants of the field.
The prophet Isaiah specifically predicted that God would lay upon the Messiah the sin of the world.
Isaiah 53:6 says, "We all, like sheep, have gone astray. Each of us has turned to his own way, and the Lord has laid on Him the iniquity of us all."
Thus, as the soldier placed a crown of thorns on the head of Jesus, this actually symbolized the spiritual reality that God was placing upon Jesus the curse of sin.
I recently heard a remarkable interpretation of the symbolic significance. The crown of thorns needs to be viewed in a Roman military context: from Wikipedia:
The grass crown (Latin: corona obsidionalis or corona graminea), was the highest and rarest of all military decorations. It was presented only to a general or commander who broke the blockade of a beleaguered Roman Army.
It's important to note that "it was presented to the general by the army he had saved".
Since the Roman company of soldiers mockingly presented this to Jesus, they unknowingly declared that he has saved them.
Pliny wrote about the grass crown:
(…), but as for the crown of grass, it was never conferred except at a crisis of extreme desperation, never voted except by the acclamation of the whole army, and never to any one but to him who had been its preserver. Other crowns were awarded by the generals to the soldiers, this alone by the soldiers, and to the general. This crown is known also as the “obsidional” crown, from the circumstance of a beleaguered army being delivered, and so preserved from fearful disaster. If we are to regard as a glorious and a hallowed reward the civic crown, presented for preserving the life of a single citizen, and him, perhaps, of the very humblest rank, what, pray, ought to be thought of a whole army being saved, and indebted for its preservation to the valour of a single individual?
The crown of thorns can be viewed as a grass crown in that: (a) the whole company presented it to Jesus, same as the whole army presenting a grass crown, and (b) it's the only award that can be given by the soldiers to the commander.
The importance of Jesus' humiliation at the hands of the world is to the Christian world a reference to Genesis, where it says that humanity shall "by the sweat of your brow [you shall] eat bread" (Genesis 3:19). Prior to his death, Jesus refers to himself as both the Bread of Life (John 6:35) and the easy yoke (Matthew 11:30). In the context of Genesis, by the sweat of our brows we will eat the bread of life, but Jesus has made the work easy by enduring it with us.
Before he received the 'crown', Jesus had been flogged, punched, and spat upon by the guards and people, which evidently would leave his whole body sweltering in the heat of the day, seeing as though he would likely be naked or mostly naked. Earlier in Gethsemane, Jesus had been praying a very emotional and surprisingly human prayer to God, begging him that if it was possible to not die, that it would come to pass (Matthew 26:39). Luke's gospel says that Jesus became so stressed that he actually sweat blood (Luke 22:44).
The idea of having a makeshift 'crown' of thorns shoved onto your head would cause your scalp and sides of your head to bleed, and since the Romans weren't aiming for the most aesthetically pleasing coronation ceremony, it is likely that the crown sat twisted a little towards one side of Jesus' head, making the thorns dig deeper into that area. He bled all over his face and sides of his head, causing the sweat on his forehead to mingle with the blood. Make of that what you will, but 'by the sweat of your brow you will eat your Bread (of Life)' sounds very prophetic in this context.
Because when he said the sower parable Matthew 13, it was meant to represent where the sower had sown the seed but the thorns had choked the plant and it died. Meaning that Jesus, his gospel is sown and the children do grow up on it but regardless they still die which testifies to his promise of eternal life, it was also meant to represent that some of the instruction the father given to Jesus to follow through the scripture was not received because he disobeyed bits of pieces, his head representing the field and the thorns on his head to show that some of the word the Father tried to sow for him to follow was choked up.
Important to note is the fact that when the Angel of the Lord(possibly Jesus Himself)and supplied a ram that was stuck in a thorn bush is reminder not only of the everlasting covenant given to Abraham but was through this lineage that Jesus was born. Take note,as Isaac was a type of Jesus being Abraham's only son,he also like Jesus CARRIED THE WOOD.Jesus carried the cross. So in essence the crown was the reminder of Him being that ULTIMATE SACRIFICIAL LAMB that Abraham sacrificed to God. Abraham at this time or after his offering to God had the vision as stated in Galations 3:8 that he was the first to receive the gospel. Wow! God is so clever. Bless you all as you gain momentum in a real hot pursuit after God's heart.
We know from Scripture that the Kings of Israel were Crowned on Passover, commencing with Saul, Israel's First King.
Rome Crowned Jesus as King of the Jews on the very day the Jewish Kings were crowned - however, this Crown represented the Curse that He was the Solution for. Therefore it was fitting that He be crowned on that Day, with that Crown.
Pilot had a sign placed over His Cross stating "Jesus of Nazareth, KING of the Jews"... fitting!
Isa 53:5 (NKJV) "He was wounded for our transgressions, He was bruised for our iniquities; The chastisement for our peace was upon Him, And by His stripes we are healed".
The 'Crown of Thorns' serves the same symbolic purpose as the 'stripes' does in the above quoted verse. This symbolic purpose is elaborated on in Isaiah chapter 58.