The Prophet ﷺ said: A fifth is payable on buried treasure.  

أَنَّ النَّبِيَّ ﷺ قَالَ فِي الرِّكَازِ الْخُمُسُ  

Al hasan said “Rikaz means treasure buried in pre Islamic times.”  

الرِّكَازُ الْكَنْزُ الْعَادِيُّ  

Al-Miqdad went to Baqi' al-Khabkhabah for a certain need. He found a mouse taking out a dinar from a hole. It then continued to take out dinars one by one until it took out seventeen dinars. It then took out a red purse containing a dinar. There were thus eighteen dinars. He took them to the Prophet ﷺ, informed him and said to him: Take its sadaqah. The Prophet ﷺ asked him: Did you extend your hand toward the hole? He replied: No. The Messenger of Allah ﷺ then said: May Allah bless you in it.  

ذَهَبَ الْمِقْدَادُ لِحَاجَتِهِ بِبَقِيعِ الْخَبْخَبَةِ فَإِذَا جُرَذٌ يُخْرِجُ مِنْ جُحْرٍ دِينَارًا ثُمَّ لَمْ يَزَلْ يُخْرِجُ دِينَارًا دِينَارًا حَتَّى أَخْرَجَ سَبْعَةَ عَشَرَ دِينَارًا ثُمَّ أَخْرَجَ خِرْقَةً حَمْرَاءَ يَعْنِي فِيهَا دِينَارٌ فَكَانَتْ ثَمَانِيَةَ عَشَرَ دِينَارًا فَذَهَبَ بِهَا إِلَى النَّبِيِّ ﷺ فَأَخْبَرَهُ وَقَالَ لَهُ خُذْ صَدَقَتَهَا فَقَالَ لَهُ ﷺ هَلْ هَوَيْتَ إِلَى الْجُحْرِ قَالَ لاَ فَقَالَ لَهُ رَسُولُ اللَّهِ ﷺ بَارَكَ اللَّهُ لَكَ فِيهَا