Jesus has just announced that one of the disciples there with him will betray him. One by one, they all denied that it could possibly be them. But in the face of a million denials, the Word of Jesus remains true and will always be fulfilled. So, Jesus repeats what he has told them.
 
20 “It is one of the Twelve,” he replied, “one who dips bread into the bowl with me. 21 The Son of Man will go just as it is written about him. But woe to that man who betrays the Son of Man! It would be better for him if he had not been born.” – Mark 14:20–21