It is narrated from Nafi‘ that Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) used to always give dates as Sadaqat al-Fitr, except for one time when he gave barley.
Imam Malik, may Allah have mercy on him, said: All expiations, charities, and zakat are to be calculated according to the smaller mudd, that is, the mudd of the Prophet, peace and blessings be upon him, except for the expiation of zihar, which is according to the larger mudd, that of Hisham bin Abdul Malik.
Hadith Referenceموطا امام مالك رواية يحييٰ / كتاب الزكاة / 701