What does Matthew 26:22 mean?

Strangely, each of the disciples asks Jesus if he is the one who will betray the Lord (Matthew 26:20–21). This comes after Jesus predicting that one of them is a traitor. On one hand, this is an extraordinary moment of humility and perspective. None of them, other than Judas (Matthew 26:14–16), have had any ill intent towards Christ at this point. Yet they all worry that Jesus' dire prophecy might apply to them. They're used to Jesus giving them difficult teachings, and they realize the possibility of falling into sin. This makes them understandably sad, thinking they could hurt their Master. In this moment, only Jesus and Judas know that Judas has taken money in exchange for an agreement to turn the Lord over to the chief priests (Mark 14:10).

Another possibility is that these questions are rhetorical: statements of innocence, rather than actual questions. In English, a common response to an accusation is "who, me?" The disciples might be saying something like "you don't think I would do that, would you?" The sorrow they express might be sadness that Jesus would even suspect such a thing. Later, Peter and others will insist their willingness to die before abandoning Christ (John 13:36–38). They will be wrong about that, though only Judas will be guilty of directly betraying Jesus to His enemies.

In an interesting detail, Judas will refer to Jesus as a teacher, rather than a master, when he speaks (Matthew 26:25). Whether Judas asks the exact same question as the others, before then, is not explicitly stated.