'The last supper' painting by Leonardo da Vinci

WHO WAS THE BETRAYER?

The Last Supper specifically portrays the reaction given by each apostle when Jesus said one of them would betray him. All twelve apostles have different reactions to the news, with various degrees of anger and shock. From left to right, according to the apostles' heads:

Bartholomew, James, son of Alphaeus, and Andrew form a group of three; all are surprised.

Judas Iscariot, Peter, and John form another group of three.

Jesus

Apostle Thomas, James the Greater, and Philip are the next group of three

Matthew, Jude Thaddeus, and Simon the Zealot are the final group of three.

Peter looks angry and is holding a knife pointed away from Christ, perhaps foreshadowing his violent reaction in Gethsemane during Jesus' arrest. He is leaning towards John and touching him on the shoulder, perhaps because in John's Gospel he signals the "beloved disciple" to ask Jesus who is to betray him.

The youngest apostle, John, appears to swoon and lean towards Peter.

Thomas is clearly upset; the raised index finger foreshadows his incredulity of the Resurrection.

James the Greater looks stunned, with his arms in the air. Meanwhile, Philip appears to be requesting some explanation.

Both Jude Thaddeus and Matthew are turned toward Simon, perhaps to find out if he has any answer to their initial questions.

Source:weiki