It is narrated from Hazrat Asma that during the blessed era of the Prophet (peace be upon him), we used to give two mudd of wheat as Sadaqat-ul-Fitr, according to the measure with which you measure.
Hadith Referenceمسند احمد / مسند النساء / 26995
Hadith Gradingحکم دارالسلام:حديث صحيح، وهذا إسناد حسن