From Webster’s Dictionary
Hearsay: unverified, unofficial information gained or acquired from another and not part of one’s direct knowledge.
Heresy: opinion or doctrine at variance with the orthodox or accepted doctrine, esp. of a church or religious system.
The reason hearsay isn’t allowed into evidence at court is because hearsay is almost always inaccurate, and often times, is woefully so.
Despite the fact God has given man many ways to communicate (written and spoken language, dialect, body language, visual aids, etc), we humans find it very hard to get our point across some times.
Truthfully I do not have the actual statistics, but I do know that even if two very intelligent people who speak the same language and come from the same background and have the very same knowledge base and dialect communicate, a portion of the information will still be lost or hopelessly distorted between them. If the receiver then tries to relay that same information to another person, even more information is lost and distorted. The more that information is relayed, the more it becomes distorted and full of holes until at last no one has any clue what the original intention was. And this is assuming all the communicators have the same intelligence, background, language, dialect, and so on. Most people don’t, and so the loss of information between communicators is even more severe.
So then, even amongst Christians who all believe in the same Bible and the same God, communication between them still causes a loss or distortion of information. Repeating that process causes yet more distortions.
Too many Christians rely on hearsay for their faith. What the preacher tells them or what their parents taught them or even what strangers in Christ have said. They do not look it up and seek God for themselves. Even if your parents had good intentions, what you thought they taught you might not be what they were really trying to teach. And who’s to know that even they got their information from the original Source? They might have passed that religious teaching down from their parents, or grandparents, or even back further through the ancestry. So one Bible lesson from great great grandpappy Tom has become so distorted and lost through the years that is now nothing close to what Old Tom was trying to teach his youngins about Jesus.
Hearsay can lead to heresy very easily. Many Christians believe and act a certain way not because God told them to do so, but because other Christians did. They believe that the word from God was brought to them undamaged and undistorted, but even with the best Christian this is impossible. My friends, trust nothing but the Source, that is, the Word of God. Test anything taught to you with the Truth that is the Word.