A.T. Robertson Commentary Matthew 26:63

"But Jesus held his peace. And the high priest said unto him, I adjure thee by the living God, that thou tell us whether thou art the Christ, the Son of God." — Matthew 26:63 (ASV)

Held his peace (εσιωπα). Kept silent, imperfect tense. Jesus refused to answer the bluster of Caiaphas.

I adjure thee by the living God (εξορκιζω σε κατα του θεου του ζωντος). So Caiaphas put Jesus on oath in order to make him incriminate himself, a thing unlawful in Jewish jurisprudence. He had failed to secure any accusation against Jesus that would stand at all. But Jesus did not refuse to answer under solemn oath, clearly showing that he was not thinking of oaths in courts of justice when he prohibited profanity. The charge that Caiaphas makes is that Jesus claims to be the Messiah, the Son of God. To refuse to answer would be tantamount to a denial. So Jesus answered knowing full well the use that would be made of his confession and claim.