At length Jesus appeared to the eleven as they were at table: and He upbraided them with their incredulity and hardness of heart, because they did not believe them who had seen Him after He was risen again. And he said to them: “Go ye into the whole world, and preach the gospel to every creature.” (Mk. 16:14-15)
In this reading we noticed how He Himself, the Lord Jesus, chided His disciples, His first members, who were always at His side, because while they were grieving at His being slain, they didn’t believe He was alive.
The fathers of the faith not yet faithful, the masters destined to bring the whole world to believe what they were going to preach and what they were going to die for, not yet believers themselves. They had seen Him raise the dead, and they didn’t believe He had risen.
So they certainly deserved to be rebuked. They were being shown to themselves, so that they might really be aware of who they were in themselves, and who they were going to be through Him.
Just as Peter, too, was shown up to himself, when on the brink of the Lord’s passion he was so sure of himself, and when as the passion commenced, he tottered and fell. He saw himself in himself, he was shocked at himself in himself, he wept at himself in himself; he turned back to the one who had made him.
And here we have these disciples not yet believing, in this reading they didn’t yet believe, when they could already see Him. What courteous consideration on His part, to have granted us the power to believe what we cannot see! We believe their words, they didn’t even believe their own eyes.
St. Augustine, Sermon 231.