٤ـ مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ ابْنِ مَحْبُوبٍ عَنِ الْحَسَنِ بْنِ صَالِحٍ الثَّوْرِيِّ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ الْسَّلام) قَالَ إِذَا كَانَ الْمَاءُ فِي الرَّكِيِّ كُرّاً لَمْ يُنَجِّسْهُ شَيْ‏ءٌ قُلْتُ وَكَمِ الْكُرُّ قَالَ ثَلاَثَةُ أَشْبَارٍ وَنِصْفٌ عُمْقُهَا فِي ثَلاَثَةِ أَشْبَارٍ وَنِصْفٍ عَرْضِهَا.
4. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from ibn Mahbub from al-Hassan ibn Salih al-Thawriy who has said the following: “Abu ‘Abd Allah , has said, ‘If a quantity of water measures one Kur it does not become unclean.’ I then asked, ‘How much is the quantity of Kur?’ He (the Imam) replied, ‘Three and a half shibr in depth and three and a half in width. ”’(A Shibr is from the tip of thumb to the tip of the small finger with the palm spread open) 