الْمَجَالِسُ بِالْأَمَانَةِ.
Matters discussed in gatherings are governed by trust.
Source: Abu Dawud (as cited in the book).
ArabicMeaning
الْمَجَالِسُgatherings; singular مَجْلِس
بِالْأَمَانَةِwith trust; under the duty of confidentiality
Repeating someone's private remarks without a legitimate reason can betray trust. The purpose of the discussion, reasonable expectations of privacy, consent, and other people's rights all matter.
A small grammar point: الْمَجَالِسُ is plural and functions as the subject; the بِـ in بِالْأَمَانَةِ is a preposition. The phrase links gatherings with the duty of trust.