Gospel According to Mark
When God uses His people to accomplish His purpose, He employs them uniquely according to their backgrounds that make up who they are, such as their educational backgrounds (as Paul), occupations (as the four Galilean fishermen, to whom Jesus said, “Follow me, and I will make you fishers of men” [Matthew 4:29]), personalities, and even past failures. Mark (or John Mark, Acts 12:12, 25; 15:37, 39) was one of those who became greatly used of the Lord because he was restored from his past failures.
Mark was a travelling companion with Paul and Barnabas on their first missionary journey (Acts 12:25; 13:5), but, for whatever the reason, he deserted the Lord’s work early on (Acts 13:13), which caused a sharp disagreement between Paul and Barnabas as to whether Mark should accompany them on their second mission trip (Acts 15:38-40). Barnabas was willing to give his cousin a second chance, but Paul refused to take him (Acts 15:39; cf. Col. 4:10).
Barnabas, “the son of consolation,” was certainly instrumental in restoring Mark, but it was Peter (as he also knew the pain of deserting the Lord and the blessedness of being restored to ministry) who developed a unique father/son relationship with Mark (1 Peter 5:13, “Marcus, my son”). In fact, it is probable that the aging Peter enlisted his “son” in the faith to write a Gospel account, for which he would supply the first-hand details.
Indeed, Peter’s fingerprints are all over the Gospel of Mark in the vivid details that only an eyewitness could have provided. It is significant that Mark paints the disciples - warts and all - as one who lived and travelled with them. On one hand, Mark also recounts the disciples’ failures more than any other Gospel. On the other hand, those brutally honest pictures of the disciples highlight Jesus’s unrelenting faithfulness to accomplish the Father’s will despite difficulties and oppositions.
Once unfaithful and labeled as “no good” for the ministry (Acts 15:38), viewing Jesus as God’s ideal Servant must have brought conviction and comfort to Mark at the same time. Paul testifies in his letters to the fact that, looking to the faithfulness of Jesus, Mark was completely healed and restored, proving himself a commendable and dependable co-laborer in the ministry, even to Paul (Phile. 24; 2 Tim. 4:11).
 See, 2 Peter 1:12-15