Albert Barnes Commentary Matthew 8:3

"And he stretched forth his hand, and touched him, saying, I will; be thou made clean. And straightway his leprosy was cleansed." — Matthew 8:3 (ASV)

And Jesus—touched him. It was an offence to the Jews to touch a leprous person, and was regarded as making the one who did so ceremonially impure (Leviticus 13:3). The act of putting forth his hand and touching him, therefore, expressed the intention of Jesus to cure him, and was a pledge that he was, in fact, already cured.