It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both), he said: Whoever listens to the conversation of a people while they dislike it, molten lead will be poured into his ears. And whoever fabricates a false dream will be compelled to tie a knot in a barley grain.
Hadith Referenceالادب المفرد / كتاب / 1167
Hadith Gradingالألبانی:صحيح الإسناد موقوفًا وقد صح مرفوعًا
Hadith Takhrij«صحيح الإسناد موقوفًا وقد صح مرفوعًا : أنظر الحديث ، رقم : 1159 - ن»
Explanation & Benefits
Shaykh Maulana Usman Muneeb
Benefits and Issues: If there are three people, it is not permissible for two of them to separate one and whisper to each other, because Satan can create the suspicion in his heart that they are talking against him. Similarly, if someone is speaking privately with another person, it is not permissible for anyone to try to listen to their conversation. Doing so is a major sin.
Source: Fadlullah al-Ahad: Urdu Commentary on al-Adab al-Mufrad, Page: 1167