Bishr bin Umar narrates: I requested Imam Malik to grant me the *Mudd* (a specific measure) of the Prophet Muhammad (peace be upon him). Imam Malik had it brought, a servant brought it and gave it to him. I showed it to Imam Malik and asked: Is this the one? He replied: Yes! This is the *Mudd* of the Prophet Muhammad (peace be upon him). Then he said: This is not the very specific measure that the Prophet Muhammad (peace be upon him) himself used, but rather it is a measure according to its measurement. (The narrator says) I asked: Do you people pay your zakat, charity, expiations, etc., according to this? He replied: Yes! We make payments according to this. I said: If a person wants to give Sadaqat al-Fitr or expiation for an oath according to the *Mudd* (which is larger than this), will it be valid? He said: No! He should pay according to this *Mudd*, and after that, he may give as much more as he wishes.
Hadith Referenceسنن الدارقطني / كتاب زكاة الفطر / 2123