Jesus touches the leper to show his might—as when God stretches out his hand (Exodus 6:6, Exodus 14:16, Exodus 15:12; Acts 4:30)—and his willingness to purify the leper by taking the leper’s uncleanness onto himself, since normally touching an unclean person made you unclean (Leviticus 13:46; Numbers 5:2).
Jesus stretches out his hand in the same manner that God does so when he does his mighty works (see Exodus 6:6, Exodus 14:16, Exodus 15:12 and Acts 4:30). Others would have simply avoided the leper because of his uncleanness, but Jesus touches him. At this particular moment, something radically changes: that whereas previously touching an unclean person led to the other party also becoming unclean (as is still the case in Judaism—see Leviticus 13:46 and Numbers 5:2), the Messiah now purifies the unclean.1
By touching the leper, Jesus, as it were, draws the uncleanness to himself. His will alone is sufficient to heal the leper in the blink of an eye.2
3 Jésus étendit la main, le toucha, et dit: Je le veux, sois pur. Aussitôt il fut purifié de sa lèpre.