Ben Sira 8:18

18 You should not do anything in front of a stranger that should be kept secret. There is no way of knowing what will happen if you do.

Ben Sira 8:18 In-Context

16 You should not get into an argument with anyone who has a hot temper or go to some place where the two of you will be alone. Violence means nothing to such a person, and he will attack you when there is no one to help you.
17 You should not ask a stupid person for advice. He will not be able to keep secret what you tell him.
18 You should not do anything in front of a stranger that should be kept secret. There is no way of knowing what will happen if you do.
19 You should not reveal your most private thoughts to anyone. If you do, you may as well throw away any chance of happiness.
Scripture taken from the Good News Translation - Second Edition, Copyright 1992 by American Bible Society. Used by Permission.