DID YOU KNOW?
The answer
Disagree. On the view most scholars hold, Matthew and Luke took such stories from Mark. So the three tellings count as one witness, not three.
Why it’s interesting
The story of the rich young man is one example: it turns up in all three Gospels. Compare the brother named James. Mark, Paul and Josephus each name him without copying one another, so that detail does count three times.
Scholarly consensus
Learn the Bible.
Not just the stories, but the history, authorship, and scholarship behind it.