Yahya related to me from Malik from Nafi from Abdullah ibn Umar that the Messenger of Allah ﷺ made the zakat of breaking the fast at the end of Ramadan obligatory on every muslim, whether freeman or slave, male or female, and stipulated it as a sa' of dates or a sa' of barley.  

أَنَّ رَسُولَ اللَّهِ ﷺ فَرَضَ زَكَاةَ الْفِطْرِ مِنْ رَمَضَانَ عَلَى النَّاسِ صَاعًا مِنْ تَمْرٍ أَوْ صَاعًا مِنْ شَعِيرٍ عَلَى كُلِّ حُرٍّ أَوْ عَبْدٍ ذَكَرٍ أَوْ أُنْثَى مِنَ الْمُسْلِمِينَ  

Yahya related to me from Malik from Zayd ibn Aslam from lyad ibn Abdullah ibn Sad ibn Abi Sarh al-Amiri that he had heard Abu Said al- Khudri say, "We used to pay the zakat al-fitr with a sa of wheat, or a sa of barley, or a sa of dates, or a sa of dried sour milk, or a sa of raisins, using the sa of the Prophet ﷺ . "  

يَقُولُ كُنَّا نُخْرِجُ زَكَاةَ الْفِطْرِ صَاعًا مِنْ طَعَامٍ أَوْ صَاعًا مِنْ شَعِيرٍ أَوْ صَاعًا مِنْ تَمْرٍ أَوْ صَاعًا مِنْ أَقِطٍ أَوْ صَاعًا مِنْ زَبِيبٍ وَذَلِكَ بِصَاعِ النَّبِيِّ ﷺ  

Yahya related to me from Malik from Nafi that Abdullah ibn Umar would always pay the zakat al-fitr in dates, except once, when he paid it in barley.  

أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ كَانَ لاَ يُخْرِجُ فِي زَكَاةِ الْفِطْرِ إِلاَّ التَّمْرَ إِلاَّ مَرَّةً وَاحِدَةً فَإِنَّهُ أَخْرَجَ شَعِيرًا  

Malik said, "Payment of all types of kaffara, of zakat al-fitr and of the zakat on grains for which a tenth or a twentieth is due, is made using the smaller mudd, which is the mudd of the Prophet ﷺ except in the case of dhihar divorce, when the kaffara is paid using the mudd of Hisham, which is the larger mudd."  

قالَ مالِكٌ: والكَفّاراتُ كُلُّها، وزَكاةُ الفِطْرِ، وزَكاةُ العُشُورِ، كُلُّ ذلِكَ بِالمُدِّ الأصْغَرِ، مُدِّ النَّبِيِّ ﷺ. إلاَّ الظِّهارَ. فَإنَّ الكَفّارَةَ فِيهِ بِمُدِّ هِشامٍ، وهُوَ المُدُّ الأعْظَمُ.