Then the high priest rent his clothes, and saith, What need we any further witnesses?
Note 9 at Mr 14:63: This was in direct defiance of God's commands. In Le 21:10, God commanded, "And he that is the high priest among his brethren, upon whose head the anointing oil was poured, and that is consecrated to put on the garments, shall not uncover his head, nor rend his clothes." Even when Aaron's two sons were struck dead by God, Moses commanded Aaron not to rend his clothes lest he die (Le 10:1-6).
This action deepens the contrast between Jesus and His accusers. They bribed one of Jesus' disciples to betray Him, held an illegal trial at night, sought false witnesses to try to make a case, and then the high priest broke the Law by rending his garment. They struck Jesus contrary to the Law they were supposed to be upholding (Ac 23:3) and mocked Jesus in a manner totally inconsistent with the principles of God's Law (Mr 14:65). They condemned Him who knew no sin while willfully committing gross sins themselves.