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 عليه السلام, 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)