Is it obligatory for a trustee to disclose a secret entrusted to him by another person, if he is asked to do so with the phrase "by your trust (or honor)," knowing that disclosing it might cause discord? And does the phrase "by your trust (or honor)" constitute an oath?

Whoever is entrusted with a secret is not permitted to disclose it, even if an oath is taken from him, because there is no obedience to a creature in disobedience to the Creator, and disclosing a secret is an act of disobedience. Abu Dawud narrated that the Prophet, peace and blessings be upon him, said: "If a man tells a narration, then turns around, it is a trust." And his saying, peace and blessings be upon him: "There is no faith for one who has no trustworthiness, and no religion for one who has no covenant."

Allah Almighty commanded the preservation and care of trusts, and preserving a secret is part of trustworthiness. Some cases are exempted from this, in which disclosing a secret is permissible. As for a person saying to another: "I entrust it to you" (or "I ask you by trust"); if he intended it as an oath, then it is an oath, and it is forbidden if it is for disclosing a secret.