The Messenger of Allah ﷺ was asked about lost property and he said, "Whatever is found on a frequented road or in an inhabited village, announce it for a year. If its owner comes, give it to him, otherwise it is yours. Whatever is not found on a frequented road or in an inhabited village, on it and on buried treasure is the fifth."
سئل رسول الله ﷺ عن اللقطة فقال: ما كان في طريق مأتي، أو في قرية عامرة فعرفها سنة، فإن جاء صاحبها وإلا فلك، وما لم يكن في طريق مأتي ولا في قرية عامرة ففيه وفي الركاز الخمس.
Nasai (2494) narrated it from Qutayba, and Abu Dawud (1712) narrated it from Musaddad, both of them from Abu Awana, from Ubaydullah bin Akhnas, from Amr bin Shuayb, with his chain of transmission, as mentioned, and the wording is that of Nasai. As for Abu Dawud, he related it in abbreviated form and did not mention the point relevant to this discussion. However, he also narrated it from Qutayba bin Saeed, who said, Layth narrated to us, from Ibn Ajlan, from Amr bin Shuayb, from his father, from his grandfather Abdullah bin Amr bin As, in a longer context, in which it says, "Whatever of it is on a well-traveled road or in a populous settlement, announce it publicly for a year. If its owner comes, give it to him, and if he does not come, it is yours. But whatever is found in ruins, meaning in it and in buried treasure, a fifth is due."Tirmidhi (1288) narrated it through this same route in abbreviated form, without mentioning the point relevant to this discussion, and he said, this is a hasan hadith. Hakim graded it sahih (2/65), and narrated it through another route, from Amr bin Shuayb, from his father, from his grandfather Abdullah bin Amr, that the Messenger of Allah ﷺ said regarding a treasure a man found, "If you found it in an inhabited settlement, or on a well-traveled path, announce it publicly. But if you found it in pre-Islamic ruins, or in an uninhabited settlement, or off the traveled path, then in it and in buried treasure a fifth is due."Hakim said, "I have provided abundant evidence in this book establishing the soundness of the narrations of Amr bin Shuayb when the one narrating from him is trustworthy, and no better narrations from him are mentioned than these. I sought clear evidence that Shuayb bin Muhammad actually heard from Abdullah bin Amr, but I have not arrived at it up to this time." End of quote.This is hasan on account of Amr bin Shuayb, and there is an important point in the chain, namely that Shuayb bin Muhammad heard from his grandfather Abdullah bin Amr bin As, and it is he who is meant when he is not named, not Muhammad, the grandfather of Amr bin Shuayb, as some might think. Moreover, this hadith of Amr bin Shuayb, from his father, from his grandfather, has been narrated with various wordings, some lengthy and some abbreviated, and many have narrated it from him, so it would not be surprising if one narration became mixed into another, and all of it is hasan.As for his saying "mati," it follows the pattern of "marmi," meaning a well-traveled road. And as for his saying "in buried treasure a fifth is due," the ruz meaning buried treasure is pre-Islamic wealth buried in the ground, and the fifth is obligatory on it due to its abundant benefit and the ease of taking it. This is what Sindi said in his marginal notes on Nasai.