From The Gospel of Mark by Mary Healy, reflecting on Mark 2:6-8:
Jesus’ word is what philosophers call a “performative statement,” a statement that brings about what it says. He is not merely telling the man that God has forgiven him; he is effecting that forgiveness. The significance of this stunning claim is not lost on the audience, some of whom are scribes trained in the law. They know well that forgiveness of sins is a prerogative of God alone (see Ps 51; Isa 43:25). Understandably, they are discomfited, and think to themselves, He is blaspheming. By perceiving these unspoken misgivings, Jesus gives the first evidence that his claim is legitimate, for it is God who reads the human heart (1 Sam 16:7; Jer 12:20; Sir 42:18).