Sahih al-Bukhari 1503
صحيح البخاري#1503SahihNarrated Ibn `Umar:Allah's Messenger (ﷺ) enjoined the payment of one Sa' of dates or one Sa' of barley as Zakat-ul-Fitr on every Muslim slave or free, male or female, young or old, and he ordered that it be paid before the people went out to offer the `Id prayer. (One Sa' = 3 Kilograms approx)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 24:103