Albert Barnes Commentary John 8:13

"The Pharisees therefore said unto him, Thou bearest witness of thyself; thy witness is not true." — John 8:13 (ASV)

Thou bearest record of thyself. You are a witness for yourself, or in your own case. See John 5:31. The law required two witnesses in a criminal case, and they alleged that as the only evidence Jesus had was His own assertion, it could not be entitled to belief.

Is not true. Is not worthy of belief, or is not substantiated by sufficient evidence.