The Messenger of Allah ﷺ made the zakat of Fitr obligatory. In the version that Malik read out, it states, "The zakat of Fitr in Ramadan is one saa of dates or one saa of barley, due upon every free person or slave, male or female, among the Muslims."
حدثنا عبد الله بن مسلمة حدثنا مالك وقرأه علي مالك أيضا عن نافع
أن رسول الله ﷺ فرض زكاة الفطر قال فيه فيما قرأه علي مالك زكاة الفطر من رمضان صاع من تمر أو صاع من شعير على كل حر أو عبد ذكر أو أنثى من المسلمين
Muslim reported it in the Book of Zakat, in the chapter on Zakat al-Fitr owed by Muslims in dates and barley, hadith no. 984, from Abdullah bin Maslama. Bukhari also reported it in the Book of Zakat, in the chapter on Sadaqat al-Fitr owed on behalf of the slave and other Muslims, hadith no. 1504, through the hadith of Malik with this same wording, and it is found in the Muwatta (Yahya's version), 1/284.