The Egerton papyrus has a version of Jesus's healing of the leper that adds further information at the beginning and end:
Egerton 1 recto (35) -- And behold, a leper came, saying, “Rabbi Jesus, I traveled with lepers and ate with them at the inn, and then I became a leper myself.”
Mark 1:40 (WEB) -- A leper came to him, begging him, kneeling down to him, and saying to him, “If you want to, you can make me clean.” Being moved with anger,* he stretched out his hand, and touched him, and said to him, “I want to. Be made clean.” When he had said this, immediately the leprosy departed from him and he was made clean. He sternly rebuked him and imme- diately threw him out, and said to him, “See that you say nothing to anybody, but go show yourself to the priest and offer for your cleansing the things which Moses commanded, for a testimony to them.”
Egerton 1 recto (47) “...and don’t keep messing up [my conjectural translation of Μηκέτι ἁμάρτανε].”
It's tempting to interpret the Egerton papyrus's prolog as preserving a record of a stage in the evolution in the understanding of disease, from the tanakh's idea that leprosy was a punishment from God to something more like our modern concept of infectious disease. (Assuming "anger" rather than "compassion" is correct, then on this reading, Jesus still has plenty of possible reasons to be annoyed with the leper.)
The Egerton papyrus's epilog is also consistent with this, since ἁμαρτάνω has the basic meaning of throwing a missile such as a spear and missing the target. This basic meaning can be expanded so that it means making a mistake in general, and I guess it's also the only word available in koine for expressing the notion of sin. So on my conjectural reading above, Jesus is simply telling the leper to stop making the mistake of exposing himself to a communicable disease, which the tanakh clearly warns is a bad idea.
This reading would become less tenable if phrases like "sin no more" and "your sins are forgiven" had clear Hebrew models in which a transgression was described using a different word than other kinds of mistakes.
Question: are there such Hebrew models (perhaps spoken by God) that are clearly the basis for Jesus's blessings and imprecations, making my reading untenable? Or are these two phrases characteristic of Jesus?
The latter phrase, e.g., in Mark 2:5, is ἀφίενταί σου αἱ ἁμαρτίαι. Again we have a person who has been cured of what we would today think of as a physical affliction, and again Jesus cures the person and talks to them about sins/mistakes. Mark is consistent in both cases by not providing a case history of how the person came to be afflicted or having Jesus show any interest in what the actual sins/mistakes were. Interestingly, the verb ἀφίημι also has a basic meaning relating to missiles (LSJ) -- to launch a missile -- but by extension (when referring to an object) to drop it or get rid of it. So on a blind translation using just the first-listed LSJ definitions, ἀφίενταί σου αἱ ἁμαρτίαι would be "your bad aiming of missiles is launched," which is obviously word salad. A more reasonable reading would be something more like "your mistakes are dumped in the garbage." LSJ does give a definition of ἀφίημι that is legal, meaning to drop a charge or punishment, so we could say "your mistakes are dropped, disposed of."
*WEB has "compassion."