"We would give Zakat Al-Fitr - when the Messenger of Allah was among us - as a Sa of food, or a Sa of barely, or a Sa of dried dates, or a Sa of raisins, or a Sa of cheese. So we did not stop paying it (like that) until Mu'awiyah arrived in Al-Madinah and talked (about it). Among the things he addressed the people with, he said: 'I see that two Mudd of the wheat of Ash-Sham are equal to a Sa of dried dates.' So the people followed that." Abu Sa'eed said: "I will not stop giving it in the manner that I had been giving it." (Using translation from Tirmidhī 673)
«كُنَّا نُخْرِجُ زَكَاةَ الْفِطْرِ إِذْ كَانَ فِينَا رَسُولُ اللَّهِ ﷺ عَنْ كُلِّ صَغِيرٍ وَكَبِيرٍ حُرٍّ وَمَمْلُوكٍ صَاعًا مِنْ طَعَامٍ أَوْ صَاعًا مِنْ تَمْرٍ أَوْ صَاعًا مِنْ شَعِيرٍ أَوْ صَاعًا مِنْ أَقِطٍ أَوْ صَاعًا مِنْ زَبِيبٍ» فَلَمْ يَزَلْ ذَلِكَ كَذَلِكَ حَتَّى قَدِمَ عَلَيْنَا مُعَاوِيَةُ الْمَدِينَةَ حَاجًّا أَوْ مُعْتَمِرًا فَقَالَ «إِنِّي أَرَى مُدَّيْنِ مِنْ سَمْرَاءِ الشَّامِ يَعْدِلُ صَاعًا مِنَ التَّمْرِ» فَأَخَذَ النَّاسُ بِذَلِكَ قَالَ أَبُو سَعِيدٍ «أَمَّا أَنَا فَلَا أَزَالُ أُخْرِجُهُ كَمَا كُنْتُ أُخْرِجُهُ» قَالَ أَبُو مُحَمَّد «أَرَى صَاعًا مِنْ كُلِّ شَيْءٍ»