Al-Kāfi

Hadith 11
water-purity
6ـ أَحْمَدُ بْنُ إِدْرِيسَ عَنْ مُحَمَّدِ بْنِ أَحْمَدَ عَنْ يَعْقُوبَ بْنِ يَزِيدَ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنْ بَعْضِ أَصْحَابِنَا عَنْ أَبِي عَبْدِ الله (عَلَيْهِ الْسَّلام) قَالَ الْكُرُّ مِنَ الْمَاءِ أَلْفٌ وَمِائَتَا رِطْلٍ.
6. Ahmad ibn Idris has narrated from Muhammad ibn Ahmad from Ya‘qub ibn Yazid from Ibn Abi ‘Umayr from certain persons of our people who has said the following: “Abu ‘Abd Allah (a.s.), has said that the quantity of one Kur of water is one thousand and two hundred ritl (a certain measurement).”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī