6. It is narrated from the narrator of the previous Hadith from his father from Safwan ibn Yahya from ‘Is ibn al-Qasim who has said the following: “I once asked abu ‘Abd Allah عليه السلام, about sleeping overnight on a flat roof without fencing wall around it. He (the Imam) said, ‘The Messenger of Allah, O Allah, grant compensation to Muhammad and his family worthy of their services to Your cause, prohibited it.’ I then asked if three yards (Zira’ arm-length) is sufficient for the height of such fencing wall. He (the Imam) said, ‘No, it is four.’ I then asked, ‘How much is the length of the wall?’ He (the Imam) said, ‘The shortest is one yard (Zira’ arm-length) and one Shibr. (the distance from the tip of the thump to the tip of the little finger with the thump and little finger open and stretched out).”’