“And, behold, there came a leper and worshipped him, saying, Lord, if thou wilt, thou canst make me clean.”
And behold, a leper came to him and knelt before him, saying, Lord, if you will, you can make me clean. The first healing after the Sermon is the healing of a leper — a person ritually unclean by the law's definition, socially isolated, excluded from the community of worship and daily life. The leper's approach is theologically precise: Lord, if you will, you can make me clean. He affirms both Jesus' power (you can) and his sovereign will (if you will) without presuming on either. The question is not whether Jesus is capable but whether he will choose to exercise that capability for a person whom the law has excluded. Leviticus 13–14 defined the leper's status and the process for potential restoration; the leper is asking Jesus to initiate what only a priest could officially declare complete.
Church Fathers on Matthew 8:2
After the preaching and teaching, is offered an occasion of working miracles, that by mighty works following, the preceding doctrine might be confirmed.
Because He taught them as one having authority, that He might not thence be supposed to use this method of teaching from ostentation, He does the same in works, as one having power to cure; and therefore, 'When Jesus descended from the mountain, great multitudes followed him.'
While the Lord taught on the mount, the disciples were with Him, for to them it was given to know the secret things of the heavenly doctrine; but now as He came down from the mount the crowds followed Him, who had been altogether unable to ascent into the mount. They that are bowed by the burden of sin cannot climb to the sublime mysteries. But when the Lord came down from the mount, that is, stooped to the infirmity, and helplessness of the rest, in pity to their…