وَعَنْ عَمْرِو بْنِ شُعَيْبٍ، عَنْ أَبِيهِ، عَنْ جَدِّهِ;
«أَنَّ اَلنَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ فِي كَنْزٍ وَجَدَهُ رَجُلٌ فِي خَرِبَةٍ-: «إِنْ وَجَدْتَهُ فِي قَرْيَةٍ مَسْكُونَةٍ، فَعَرِّفْهُ، وَإِنْ وَجَدْتَهُ فِي قَرْيَةٍ غَيْرِ مَسْكُونَةٍ، فَفِيهِ وَفِي اَلرِّكَازِ: اَلْخُمُسُ»
The Messenger of Allah (sallallahu alayhi wa sallam) was asked about a treasure that was found by a man in some ruined land, and he said to him, ‘If you found it in an inhabited village, then you must advertise its having been found. However, if he found it in an uninhabited village, then on it and the rest of the discovered treasure one fifth is payable as Zakah.’ Related by Ibn Majah with a reliable chain of narrators.’
Bulugh al-Maram 733, Book 4, The Book of Zakah, Hadith 27. 1 min read