What does Mark 15:31 mean?
The irony of the priests' and scribes' words can't be overstated. "Save" comes from the Greek root word sozo. Primarily, it means to keep safe from harm, disease, or death, but it also means to save from God's judgment. Jesus is the only man on earth who should be safe from God's judgment.The chief priests and scribes should know this. Both groups claim to be experts of the Mosaic law and the Jewish Scriptures, what we call the Old Testament. They have all the information they need to recognize the coming of the Messiah, whom God promised to save Israel (John 5:39–40). Through either negligence, self-delusion, or extreme reluctance to surrender their worldly status, they refuse to accept Jesus is the Messiah. This is why Jesus tells Pilate, "You would have no authority over me at all unless it had been given you from above. Therefore he who delivered me over to you has the greater sin" (John 19:11).
Jesus came to earth specifically to be bear God's judgment so that people like these chief priests and scribes can be safe. During Jesus' sacrifice on the cross, He bears the judgment of the sin of mankind. He is not on the cross because He cannot save Himself. He is there voluntarily, to save others. And Only when He is finished will He save Himself (John 10:17–18).