Hazrat Mutarrif narrates that I was present in the service of Sayyiduna Uthman bin Abi al-As (may Allah be pleased with him), so he called for milk to be brought for me to drink. I said, "I am fasting." He said: "Indeed, I heard the Messenger of Allah (peace and blessings be upon him) say that 'Fasting is a shield from Hell just as a shield is for any one of you in battle.'" And he said: "The best fasting is to fast three days in every month."