Matthew 8:
1 When he came down from the mountain, great crowds followed him.
2 And behold, a leper came to him and knelt before him, saying, “Lord, if you will, you can make me clean.”
3 And Jesus stretched out his hand and touched him, saying, “I will; be clean.” And immediately his leprosy was cleansed.
4 And Jesus said to him, “See that you say nothing to anyone, but go, show yourself to the priest and offer the gift that Moses commanded, for a proof to them.”
Jesus stretched out his hand and touched him
Leviticus 13:45–46
The leprous person who has the disease shall wear torn clothes and let the hair of his head hang loose, and he shall cover his upper lip and cry out, ‘Unclean, unclean.’ He shall remain unclean as long as he has the disease. He is unclean. He shall live alone. His dwelling shall be outside the camp.
While most would have shied away from any contact or even general interaction with a leper, Jesus displays the love and mercy of God by reaching out and touching this man. When Elisha healed Naaman the leper (2 Kings 5), he did not greet Naaman in person but rather did so by a word sent through his messenger.
Miracles of healing also symbolize forgiveness of sins. God's word remains the saving power today as in the day of Elisha, but in Jesus we have received mercy and grace, as well. Jesus knows what it is to be in the flesh, and is sympathetic to our needs.
Hebrews 4:15
For we do not have a high priest who is unable to sympathize with our weaknesses, but one who in every respect has been tempted as we are, yet without sin.
say nothing to anyone
Several times in the gospels Jesus instructs people to keep what He has done for them quiet. Mark 1:45 (below) explains why this is.
the gift that Moses commanded
The gift to which Jesus refers is captured in Leviticus 14:1–20, with an alternative option for the poor in verses 21–32.
The fact that provision is made, "…if he is poor and cannot afford so much" (v.21), tells us the offering was a hefty amount. A leper who has been healed has much to be thankful for.
for a proof
The phrase rendered "for a proof" (εἰς μαρτύριον) is literally, "as a witness" or "as a testimony." At first blush, one might be tempted to think think this phrase merely refers to Leviticus, since the "Tent of Meeting" (Leviticus 1:1) was literally a "Tent of Witness" or "Tent of Testimony." But the phrase "for a witness" does appear elsewhere in Scripture, and its use in these other places helps us understand what is meant here.
The phrase appears again in Matthew 10:18, "You will be dragged before governors and kings for my sake, to bear witness before them and the Gentiles." In that verse it's clear the reason the apostles appear before governing authorities is so that they may testify about Jesus. Matthew 8:4, thus, could be rendered, "offer the gift Moses commanded, so as to testify to them."
Even more compelling, though, is the thought captured in Hebrews 3:1–8. In that passage, it is clear that Moses proved faithful in everything for a specific purpose: to bear witness to what would be spoken later in Christ. Thus, Moses serves Christ, laying the groundwork for His coming.
Hebrews 3:1–8
Therefore, holy brothers, you who share in a heavenly calling, consider Jesus, the apostle and high priest of our confession, who was faithful to him who appointed him, just as Moses also was faithful in all God’s house. For Jesus has been counted worthy of more glory than Moses—as much more glory as the builder of a house has more honor than the house itself. (For every house is built by someone, but the builder of all things is God.) Now Moses was faithful in all God’s house as a servant, to testify to the things that were to be spoken later, but Christ is faithful over God’s house as a son. And we are his house, if indeed we hold fast our confidence and our boasting in our hope. Therefore, as the Holy Spirit says, “Today, if you hear his voice, do not harden your hearts….”
In Matthew 8:4, then, Jesus excels Moses by directly healing leprosy without having to follow the procedures of Leviticus. The priests should be able to discern this fact, and they should conclude that something greater than Moses is here.