2. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from certain persons of his people from Aban from Muhammad al- Halabiy who have said the following: “Abu ‘Abd Allah, ‘Alayhi al-Salam, has said, ‘It is not lawful for one to sell with a Sa‘ which is not in use in a city. A man may hire a camel man and measures with a device of his home which perhaps is smaller than the mud (a certain measurement) of the market- place. If he says it is smaller than the mud of the market he does not accept unless he guarantees and takes responsibility thereof.’ He (the Imam) said, ‘There must be one mud. Taking responsibility also serves this purpose.’”