Matthew 26:21 - Ellicott's Commentary On The Whole Bible

One of you shall betray me. — The words would seem to have been intentionally vague, as if to rouse some of those who heard them to self-questioning. They had not, it is true, shared in the very guilt of the Traitor, but they had yielded to tendencies which they had in common with him, and which were dragging them down to his level. They had joined him in his murmuring (Matthew 26:8), they had been quarrelling, and were about to renew their quarrel, about precedence (Mark 9:34; Luke 22:24). It was well that the abyss should be laid bare before their eyes, and that each should ask himself whether he were indeed on the point of falling into it.