Contradiction with Matthew 8:4
Mark 1:43 involves Jesus instructing the healed leper to tell no one, while Matthew 8:4, recounting the same event, includes explicit instructions for the leper to show himself to the priest and offer the gift Moses commanded as a testimony to them.
Matthew 8:4: And Jesus saith unto him, See thou tell no man; but go thy way, shew thyself to the priest, and offer the gift that Moses commanded, for a testimony unto them.