Q: An extremely wise guru, renowned by some as a saint, has taught that if a guru teaches nine things you agree with, and one you are unsure about, then it is wise to accept that extra one on faith.
A: Do you believe that on faith? I sincerely hope this "wise guru" of yours did not say that, or that you misunderstood his teaching; but I fear you may have heard him correctly.
I repeat, you should take nothing on faith. Learn to examine each item individually and on its own merits. If you are unsure about that tenth item, then you should give it special examination, but whatever you do, do not believe it! It is always that tenth item which distinguishes the true gurus from the impostors. It is easy to speak many small truths, and it is equally easy to fall down on the big ones. If a guru teaches nine things you agree with, and one that you know to be wrong, then you would do well to review the previous nine in the light of the tenth!
Watch how you go. The disciple, in following his master, should be careful not to tread upon his masters shadow. Keep your distance! Beware lest ye be crushed by a falling statue!