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