For a testimony unto them
"And, behold, there came a leper and worshipped him, saying, Lord, if thou wilt, thou canst make me clean." – Mathew 8:2 (KJV)
What did the leper mean by "if thou will"?
He came and worshipped Jesus. Perhaps he knew this wasn't just another prophet; perhaps he knew this was God, come in the flesh.
He knew that this man could heal him from the inside out. He knew Christ could heal his sinful nature, make him clean from leprosy of the heart that caused leprosy on his flesh.
"go thy way, show thyself to the priest, and offer the gift that Moses commanded, for a testimony unto them." - Matthew 8:4 (KJV)
The priest, with all the rituals, couldn't fulfill the law nor could he make the sinner clean. They had to recall their sins every year and the sinner always remained a sinner; the lost remained lost and the leper remained a leper.
This was an imperfect priesthood carried out by sinful men, ready to be abolished.
Jesus is sending this man to let the priest know that his office is going to be closed soon.
"In that he saith, A new covenant, he hath made the first old. Now that which decayeth and waxeth old is ready to vanish away." - Hebrews 8:13 (KJV)
Jesus, the Great High Priest is the fulfillment of the law. He makes the sinner clean, removes sin and the underlying nature of it and cleanses the condition of the heart.
The sinner is transformed to saint; the lame man is made to walk, leap and praise God; and the leper is made whole.
Jesus Christ is The Great High Priest, ever interceding for me and you.
"Lord, if you will, you can make me clean. Cleanse my heart oh gracious Lord, make me like you, worthy of your name."
Robin S. Jacob