Greeted with 'My Friend'

Matthew 26:48-50
48The traitor, Judas, had given them a prearranged signal: “You will know which one to arrest when I greet him with a kiss.” 49So Judas came straight to Jesus. “Greetings, Rabbi!” he exclaimed and gave him the kiss.
50Jesus said, “My friend, go ahead and do what you have come for.”