What does John 5:42 mean?

Jesus knows that these men are not following the will of God for a basic reason: they have rejected the One God sent (John 5:38). This rejection is not based on reason or evidence. Jesus has the support of human testimony (John 5:33), miracles (John 5:36), and the written Word of God (John 5:39). The evidence is there, but the men who deny Christ do so in "refusal" (John 5:40). They have made up their minds and so no proof will ever be enough to change their hearts.

Ultimately, one cannot truly love God if they ignore His words (John 5:46) or His messenger (John 5:23). The opening lines of the Gospel of John described Jesus as a light who came into the world (John 1:9–11). The reason men reject this light is not because they can't see it, but because they prefer darkness (John 3:19). The Bible is clear that those who truly seek God will accept Christ (Matthew 7:7–8) because He is the one and only way to be reconciled with the Father (John 14:6). Any claims these men made to loving God were contradicted by their own actions and their refusal to accept God's Son.