Origen
Catena Aurea · Matthäusevangelium 26
And while he yet spake, lo, Judas, one of the twelve, came, and with him a great multitude with swords and staves, from the Chief Priests and elders of the people. Now he that betrayed him gave them a sign, saying, Whomsoever I shall kiss, that same is he: hold him fast. And forthwith he came to Jesus, and said, Hail, Master; and kissed him. And Jesus said unto him, Friend, wherefore art thou come? Then came they, and laid hands on Jesus, and took him.
If it be asked why Judas betrayed Jesus with a kiss, according to some it was because He desired to keep up the reverence due to his Master, and did not dare to make an open assault upon Him; according to others, it was out of fear that if he came as an avowed enemy, he might be the cause of His escape, which he believed Jesus had it in His power to effect. But I think that all betrayers of truth love to assume the guise of truth, and to use the sign of a kiss. Like Judas also, all heretics call Jesus Rabbi, and receive from Him mild answer. And Jesus said unto him, Friend, wherefore art thou come? He says, Friend, upbraiding his hypocrisy; for in Scripture we never find this term of address used to any of the good, but as above, Friend, how camest thou in hither? (Matt. 22:12.) and, Friend, I do thee no wrong. (Matt. 20:13.)