Hadith 659B

قَالَ مَالِك : الْأَمْرُ الَّذِي لَا اخْتِلَافَ فِيهِ عِنْدَنَا وَالَّذِي سَمِعْتُ أَهْلَ الْعِلْمِ يَقُولُونَهُ : إِنَّ الرِّكَازَ إِنَّمَا هُوَ دِفْنٌ يُوجَدُ مِنْ دِفْنِ الْجَاهِلِيَّةِ ، مَا لَمْ يُطْلَبْ بِمَالٍ وَلَمْ يُتَكَلَّفْ فِيهِ نَفَقَةٌ وَلَا كَبِيرُ عَمَلٍ وَلَا مَئُونَةٍ ، فَأَمَّا مَا طُلِبَ بِمَالٍ وَتُكُلِّفَ فِيهِ كَبِيرُ عَمَلٍ فَأُصِيبَ مَرَّةً وَأُخْطِئَ مَرَّةً فَلَيْسَ بِرِكَازٍ
Imam Malik, may Allah have mercy on him, said: There is no difference of opinion in this matter according to us, and I have also heard from the people of knowledge that rikaz is a buried treasure from among the treasures of the disbelievers, when it is found without much effort and without spending money. So if it is found by spending money or with great effort, and sometimes it is found and sometimes not, then it will not be called rikaz.
Hadith Reference موطا امام مالك رواية يحييٰ / كتاب الزكاة / 659B
Hadith Takhrij «شركة الحروف نمبر: 536، فواد عبدالباقي نمبر: 17 - كِتَابُ الزَّكَاةِ-ح: 9»