Jesus heals a man with leprosy.
v.1 Jesus has completed the Sermon on the Mount (ch.5-7) and now will demonstrate his messianic mission with deeds. Jesus came down from the mountain (cf. 5:1) and large crowds followed him since they were amazed at his teaching (7:28).
(For v.2-4 see parallels in Mk 1:40-44 and Lk 5:12-14.)
v.2-3 The first miracle in this section is of a leper. The leper shows faith in Jesus and knelt before him calling him Lord. Jesus reaches out to him and heals him immediately. For lepers to be made clean is a mark of the Messiah (11:2-6).
v.4 Jesus implores him to tell no one, but show himself to the priest (Lv 14:1-32), presenting an offering, as a witness to them.

Read Matthew 8:1-4