Knowledge plays a part in the man's healing; this theme is suggested by the fact that each of the parties claim both to know and not to know something. Since the claims and the reasons for them differ, the contrasts highlight their various types of knowledge. By their questioning, the Pharisees try to discredit the man's testimony, attempting to find a cause to brand the healing a fraud and to attack Jesus (verse 19). They imply that the parents should stop lying and come clean (verses 20-21). Yet, the parents affirm two facts: that the healed man was indeed their son and that he was born blind. They knew this, and they were not afraid to affirm it.
Conversely, they denied knowing how he came to see and who did the miracle. Why do they not acknowledge what they know of Christ's role in the healing? “They feared the Jews.” They know that the leaders would excommunicate anyone who confessed Jesus as the Messiah. The parents simply did not want to get involved. They were afraid to acknowledge what had been revealed to them.
This is an accurate picture of many today. The truths of Christianity have been proclaimed to them—perhaps by parents, friends, or the church. Intellectually, they know and even believe these truths, but they will not admit them. They are afraid to acknowledge Christ for fear of the consequences.
Martin G. Collins
The Miracles of Jesus Christ: Healing a Man Born Blind (Part Three)