Even while he was still speaking, Judas, one of the Twelve, came up with a number of men armed with swords and clubs, sent by the chief priests and the scribes and the elders. Now the traitor had arranged a signal with them. ‘The one I kiss,’ he had said ‘he is the man. Take him in charge, and see he is well guarded when you lead him away.’
So when the traitor came, he went straight up to Jesus and said, ‘Rabbi!’ and kissed him.
Mark 14: 43-46 (Jerusalem Bible)