Alternative rephrasing from a source without a citation:
"Do not believe in anything simply because you have heard it. Do not believe in anything simply because it is spoken and rumored by many. Do not believe in anything simply because it is found written in your religious books. Do not believe in anything merely on the authority of your teachers and elders. Do not believe in traditions because they have been handed down for many generations.
But after observation and analysis, when you find that anything agrees with reason and is conducive to the good and benefit of one and all, then accept it and live up to it."
Most people underestimate how valuable personal anecdotes are compared to sampling/survey data. Has it ever happened to you that a restaurant or other experience has thousands of rave reviews online (or even among your friends) but when you go there it's shockingly underwhelming? That happens a lot. Your personal anecdote is almost always more valuable in such cases because of several reasons including recency, authenticity, self-honesty and the usual problems with review aggregation platforms.
Food is a very subjective thing, online reviews generally are often intentionally or unintentionally distorted, and quality/staff at those places changes too over time. Considering all these factors, that does not make this specific scenario a great more general example
It is Buddha telling the traders that they shouldn't trust whatever is told to them even if it comes from the so-called experts/gurus, family/friends, teachers, traditions etc. He told them that they should try to reason out the things being told to them, give these a try in their lives and only keep them if these suggestions/advice works for them. A more simplified version can be found here too: https://www.ling.upenn.edu/~beatrice/personal/buddhist-pract...
