Mark is the only evangelist who recorded this miracle. It corresponds to the healing of the deaf man with the speech impediment ( Mark 7:31-36), the only other miracle that Mark alone recorded. This is the only miracle in Mark that was not instantaneous; it happened gradually. Sight is a common metaphor for understanding. The disciples should have seen the deaf man as a picture of themselves unable to comprehend what Jesus said. This blind man also represented them in their inability to understand what Jesus showed them (cf. Mark 8:21). Jesus could and would make them whole, as He healed these two physically limited men. [source][source][source]