Bukhari

Takhrij:
[بخاري 7042 كتاب التعبير باب من كذب فى حلمه]
In the copies of Bulugh al-Maram, the wording is «من تسمع», whereas in Bukhari, the wording is «استمع». The meanings are almost the same.

Benefits:
Eavesdropping on someone’s private conversation, when they dislike it, is forbidden (haram). From this hadith, it is understood that if people are conversing among themselves and do not like someone else to listen, then it is haram to eavesdrop on their conversation. This is because such a severe punishment—having molten lead poured into the ears—cannot be for a merely disliked (makruh) act.

Now, how can it be known that they do not like someone to listen? This is understood from circumstantial evidence. First of all, if two or more people are sitting somewhere in seclusion, it is clear that they do not want anyone else to participate in their conversation. Sometimes, they even explicitly express their displeasure. Now, after it becomes clear from circumstantial evidence or explicit words that they are displeased, if someone tries to listen secretly or by any means, then molten lead will be poured into his ears, because this sin was committed through the ears.

Sa‘id al-Maqburi says: I passed by Ibn ‘Umar radi Allahu anhuma, and there was a man standing with him, talking to him. I also stood by them, so Ibn ‘Umar radi Allahu anhuma pushed me in the chest and said: When you see two men talking, do not stand by them without permission. [مسند احمد و سنده صحيح حديث نمبر 5949 تحقيق احمد شاكر]

From this hadith, it is also understood that if those conversing among themselves, upon being asked for permission, grant it, but it is apparent to the person that they did so out of shyness or reluctance and do not truly want him to listen, then it is still not permissible for him to eavesdrop on their conversation.

Some people sit a little distance away and, after hearing a word or two, deduce the rest themselves; such people are also included in this warning. Similarly, peeking into someone’s house, sniffing, or spying is also haram. It is also haram to keep asking children about matters of the house that the householders do not like to be disclosed. However, if it is known through a reliable source that these people are planning a sin or oppression, then listening for the purpose of forbidding evil (nahi ‘an al-munkar) is permissible.

Takhrij:
«أخرجه البخاري، التعبير، باب من كذب في حلمه، حديث:7042.»©Explanation:
In this hadith, there is a prohibition against a person seeking out, with great attention, effort, and diligence, to listen to the secrets and confidential matters of another individual or group (which they do not wish to disclose in front of others).
On the Day of Resurrection, molten lead will be poured into the ears of such a person.
This is one of the etiquettes of gatherings that should be observed.
Imam al-Bukhari rahimahullah has narrated in his book "al-Adab al-Mufrad" from Sa'id al-Maqburi, who says that Ibn 'Umar radi Allahu anhuma was conversing with a man, and I came and stood near them. Ibn 'Umar radi Allahu anhuma struck my chest and said: "When two people are conversing privately, do not listen to their conversation; this is prohibited."
(al-Adab al-Mufrad, Chapter: If you see people conversing privately, do not join them: 2/660, Hadith no. 1166, Maktabat al-Ma'arif, Riyadh edition) In any case, it is not permissible to interfere in someone’s confidentiality.