A.T. Robertson Commentary Luke 22:67

"If thou art the Christ, tell us. But he said unto them, If I tell you, ye will not believe:" — Luke 22:67 (ASV)

If thou art the Christ (Ε συ ε ο Χριστος). The Messiah, they mean. The condition is the first class, assuming it to be true.

If I tell you (Εαν υμιν ειπω). Condition of the third class, undetermined, but with likelihood of being determined. This is the second appearance of Jesus before the Sanhedrin merely mentioned by Mr 15:1; Matthew 27:1 who give in detail the first appearance and trial. Luke merely gives this so-called ratification meeting after daybreak to give the appearance of legality to their vote of condemnation already taken (Matthew 26:66).

Ye will not believe (ου μη πιστευσητε). Double negative with the aorist subjunctive, strongest possible negative. So as to verse 68.