A.T. Robertson Commentary Matthew 26:50

"And Jesus said unto him, Friend, [do] that for which thou art come. Then they came and laid hands on Jesus, and took him." — Matthew 26:50 (ASV)

Do that for which thou art come (εφ' ο παρε). Moffatt and Goodspeed take it: "Do your errand." There has been a deal of trouble over this phrase. Deissmann (Light from the Ancient East, pp. 125 to 131) has proven conclusively that it is a question, εφ' ο in late Greek having the interrogative sense of επ τ (Robertson, Grammar, p. 725). The use of εφ' ο for "why here" occurs on a Syrian tablet of the first century A.D. 50 that it "was current coin in the language of the people" (Deissmann). Most of the early translations (Old Latin, Old Syriac) took it as a question. So the Vulgate has ad quid venisti. In this instance the Authorized Version is correct against the Revised. Jesus exposes the pretence of Judas and shows that he does not believe in his paraded affection (Bruce).