What does John 8:43 mean?

Here, again, Jesus makes a point He has already taught. Those who cannot understand the will of God, or the message of God, are those who do not want to understand. The problem is not their intellect or their learning. The problem is that they are committed to rejecting what they do not want to hear. Their intent overrides all evidence, logic, and spiritual humility (John 7:17). Jesus has pointed out that these men have access to the Scriptures (John 5:39–40), have witnessed His miracles (John 5:36; John 8:18; John 3:1–2), have heard human testimony (John 5:33–34), and have heard the very words of One who came from heaven (John 8:23).

This obstinate attitude is rooted in their nature; nature is something man inherits through a father. According to these religious leaders, their father is Abraham (John 8:33). As Jesus pointed out, however, their actions suggest something very different. Abraham might be their earthly ancestor, but he is not their spiritual father. Those who are "true sons" of Abraham would do what Abraham did—obey God (John 8:39–41). These men deal in lies and violence (John 5:18). Jesus has made several subtle references to some "other" father (John 8:38), and His critics have responded by calling Him an illegitimate child (John 8:41).

In the next verse, Jesus will complete His crushing condemnation of these men by pointing out their true spiritual father, who is both a liar and a murderer (John 8:44).