The Messenger of Allah ﷺ made the Zakat of Fitr obligatory, one saa, and he then mentioned it with the same meaning as Malik's narration, adding "the young and the old," and he commanded that it be paid before the people went out to the prayer.
حدثنا يحيى بن محمد بن السكن حدثنا محمد بن جهضم حدثنا إسمعيل بن جعفر عن عمر بن نافع عن أبيه
فرض رسول الله ﷺ زكاة الفطر صاعا فذكر بمعنى مالك زاد والصغير والكبير وأمر بها أن تؤدى قبل خروج الناس إلى الصلاة
Bukhari narrated it, in the Book of Zakat, Chapter on the obligation of Zakat al-Fitr, no. 1503, from Yahya bin Muhammad Ibn Sakan with this chain. Muslim also narrated it, in the Book of Zakat, Chapter on Zakat al-Fitr being due from Muslims in dates and barley, no. 984, from the hadith of Nafi with this chain.