(78) باب صَدَقَةِ الْفِطْرِ عَلَى الصَّغِيرِ وَالْكَبِيرِ
Narrated Ibn `Umar:
Allah's Messenger (ﷺ) has made Sadaqat-ul-Fitr obligatory, (and it was), either one Sa' of barley or one Sa' of dates (and its payment was obligatory) on young and old people, and on free men as well as on slaves.
Reference: Sahih al-Bukhari 1512
In-book reference: Book 24, Hadith 113
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 2, Book 25, Hadith 588