And while He was still speaking, behold, Judas, one of the twelve, with a great multitude with swords and clubs, came from the chief priests and elders of the people.  Now His betrayer had given them a sign, saying, "Whomever I kiss, He is the One; seize Him." 

Immediately he went up to Jesus and said, "Greetings, Rabbi!" and kissed Him. 

But Jesus said to him, "Friend, why have you come?"

Then they came and laid hands on Jesus and took Him. 

Matthew 26:47-50  (NKJV)