Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
bukhari:1510Muʿādh b. Faḍālah > Abū ʿUmar > Zayd > ʿIyāḍ b. ʿAbdullāh b. Saʿd > Abū Saʿīd al-Khudrī

In the lifetime of Messenger of Allah ﷺ , we used to give one Sa' of food (edible things) as Sadaqat-ul-Fitr (to the poor). Our food used to be either of barley, raisins (dried grapes), cottage cheese or dates.  

البخاري:١٥١٠حَدَّثَنَا مُعَاذُ بْنُ فَضَالَةَ حَدَّثَنَا أَبُو عُمَرَ عَنْ زَيْدٍ عَنْ عِيَاضِ بْنِ عَبْدِ اللَّهِ بْنِ سَعْدٍ

عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ ؓ قَالَ كُنَّا نُخْرِجُ فِي عَهْدِ رَسُولِ اللَّهِ ﷺ يَوْمَ الْفِطْرِ صَاعًا مِنْ طَعَامٍ وَقَالَ أَبُو سَعِيدٍ وَكَانَ طَعَامَنَا الشَّعِيرُ وَالزَّبِيبُ وَالأَقِطُ وَالتَّمْرُ