Commissioning the Disciples
"Afterward [Jesus] appeared to the eleven themselves as they were reclining at table, and he rebuked them for their unbelief and hardness of heart, because they had not believed those who saw him after he had risen. And he said to them, 'Go into all the world and proclaim the gospel to the whole creation.'"
Mark's gospel makes it quite clear that it was not because of the disciples' great faith that Jesus called them to follow Him during His earthly ministry. Even after they saw Jesus perform miracles such as feeding thousands of people with only a handful of fish and loaves (which they saw twice), the hearts of the disciples were hard and did not truly grasp who He was (Mark 6:30–44, 52; 8:1–10, 17). The disciples were so slow to believe that even Peter, whose confession at Caesarea Philippi reveals that he had greater insight into Jesus' identity than the others did, failed to believe what Christ said about the necessity of His death and resurrection (8:27–33). This disbelief continued past our Lord's rising again from the dead, for the longer ending of Mark's gospel makes it plain that their lack of trust endured even when witnesses to the resurrection proclaimed the empty tomb to them (16:9–13).
Doubt and unbelief are not minor sins, as we see in today's passage. When Jesus finally appeared visibly to the eleven disciples after His resurrection (Judas had committed suicide before this; see Matt. 27:3–10), He rebuked them for their lack of faith (Mark 16:14). Note that Jesus did not excuse their unbelief for lack of evidence of His resurrection or because the testimony of the witnesses was inadequate. He fully expected them to believe before they could see Him with their own eyes. No, Jesus did not excuse them because of the absence of proof, for there was evidence of His resurrection, including the empty tomb and the words of Mary Magdalene and others. He rebuked them because they failed to receive the news of His resurrection on account of their hardness of heart. When people disbelieve the gospel, it is not because the gospel lacks proof; it is because they love their sin. Matthew Henry comments, "The evidences of the truth of the gospel are so full, that those who receive it not, may justly be upbraided with their unbelief; and it is owing not to any weakness or deficiency in the proofs, but to the hardness of their heart, its senselessness and stupidity."
Even those who follow Jesus may fall into doubt and unbelief, and we should fight against these transgressions. But thanks be to God—these sins, while serious, are not disqualifying sins. After all, the same men whom Jesus rebuked for their doubt He then commissioned to preach His gospel to all the world (Mark 16:15). Past failures to believe do not mean we cannot be used of God today.
Coram Deo
Many Christians go through periods of doubt and think that this makes them unable to serve the Lord or to be used by Him to do great things. We dare not believe such untruths, however. What matters is whether we trust Christ in the present. If we trust Him today, He can use us for the good of His kingdom no matter how we have failed in the past.