Was there any difference between John Mark leaving Paul and Barnabas during their earlier missionary trip and Demas leaving Paul now?
It was in John Mark's mother's home where they had the all night prayer meeting for Peter's release from prison (Acts 12). John Mark was Barnabas' nephew, and had seen and experienced miracles. His ministry was undoubtedly different than Paul's. Barnabas understood this, but Paul had been irritated when John Mark had gone off on his own (Acts 15). Perhaps, John Mark would have been wiser to finish the trip, but he did not forsake God.
Demas, on the other hand, walked away from the faith because he stumbled over the things in the world. It is quite possible that Paul had Demas in mind when he wrote to Timothy, "they will not endure sound doctrine but according to their own desires, because they have itching ears, they will heap unto themselves teachers; they will turn away their ears from the truth, and be turned aside to fables" (2 Timothy 4:3-4).
Paul felt the pain of Demas forsaking the truth. "Be diligent to come to me quickly, for Demas has forsaken me..." It can be devastating when someone we know, no longer serves God. We need the comfort and strength that comes from one another.
