21. Ali ibn Ibrahim has narrated from his father from ‘Abd Allah ibn al-Mughirah from ‘Abd Allah ibn Sinan who has said the following: “This is concerning my question before abu ‘Abd Allah عليه السلام, about buying gold in which there was silver, mercury and soil in exchange for dinars and wariq (dirham). He (the Imam) said, ‘You must not change except with wariq (dirham).’ I then asked him (the Imam) about buying silver in which there was lead and wariq (dirham). If it was pure it was reduced by two or three dirhams of each ten. He (the Imam) said, ‘It is not valid except for gold.’”