What does John 5:33 mean?

After Jesus heals a man on the Sabbath (John 5:1–15), local religious leaders are furious. Rather than being amazed at the miracle, these cold-hearted men are angry about Jesus violating their traditions and claiming equality with God (John 5:18). Jesus responds by explaining that He is, in fact, equal to God and gives specific examples (John 5:19–29).

After this, Jesus acknowledges that certain claims require evidence (John 5:31). And, rather than appeal to blind faith, Jesus provides exactly that evidence. In verses 32 and 33, Jesus refers to the first of His three forms of evidence: human testimony. Specifically, Jesus refers to the testimony of John the Baptist. The Gospel of John has already recorded investigators from the Pharisees approaching John the Baptist (John 1:19–24) and his profession of Jesus as the Messiah (John 1:25–28). Since Jesus has a unique perspective, the truth of His testimony does not literally depend on the input of other people (John 5:34; 8:14). However, He acknowledges the natural human need for confirmation.

Jesus will also mention two other forms of evidence, which are His miracles (John 5:36) and the written Scriptures (John 5:39).