The Thirty Pieces of Silver
Judas went of his own accord to the chief priests and asked, "what will you give me if I hand him over to you?" They gave him thirty pieces of silver — the price of a slave in the Hebrew Bible, by which the New Testament writers hint at the nature of the bargain. From then on Judas watched for a chance to hand Jesus over.
The Kiss in Gethsemane
Judas led those who came to seize Jesus into the Garden of Gethsemane, having arranged beforehand that "the one I kiss is the man," and stepped forward calling "Rabbi" and kissing Jesus, whereupon the soldiers arrested him. This betrayal completed by an act of intimacy made "the kiss of Judas" a classic image of "outward closeness that is inwardly betrayal."