But Jesus held his peace. And the high priest answered and said unto him, I adjure thee by the living God, that thou tell us whether thou be the Christ, the Son of God.
Note 5 at Mt 26:63: Only Matthew recorded that the high priest commanded Jesus under oath to answer his questions. This shows the frustration of the high priest. This mock trial was not going well for Jesus' opponents. All of their so-called evidence had failed to prove anything. Out of desperation, they tried to make Jesus say something that they could use against Him.
If Jesus had refused to talk, the Sanhedrin (see note 11 at Mt 5:22) would have had to let Him go, as they had failed to prove any guilt. Jesus voluntarily spoke truths that He knew would seal His death. This illustrates once again that no man took Jesus' life from Him; He gave it (see note 3 at Mt 26:54).