2. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from Muhammad ibn Sahl from Zakariya ibn Adam who has said the following: “I once asked abu al-Hassan, al-Rida , about a fistula (a bad wound) if it invalidates Wudu’ or not. He (the Imam) said, ‘Only three things invalidate Wudu’: urine, feces and gas.’”