Al-Kāfi - Volume 5 > Impure Dirhams (Certain Silver or Gold Coins)
Hadith #4

4- مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ الْبَرْقِيِّ عَنِ الْفَضْلِ أَبِي الْعَبَّاسِ قَالَ سَأَلْتُ أَبَا عَبْدِ اللهِ (عَلَيْهِ السَّلام) عَنِ الدَّرَاهِمِ الْمَحْمُولِ عَلَيْهَا فَقَالَ إِذَا أَنْفَقْتَ مَا يَجُوزُ بَيْنَ أَهْلِ الْبَلَدِ فَلا بَأْسَ وَإِنْ أَنْفَقْتَ مَا لا يَجُوزُ بَيْنَ أَهْلِ الْبَلَدِ فَلا.

4. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from al-Barqiy from al-Fadl ibn al-‘Abbas who has said the following: “This is concerning my question before abu ‘Abd Allah, ‘Alayhi al-Salam, about dirhams with impurities. He (the Imam) said, ‘If you spend what is permissible to spend among people in a city, it is not unlawful; but if you spend what is not lawful to spend among the people of a land, then it is not permissible.’”