Sahih al-Bukhari 1512
Sahih al-Bukhari · Book 24: Obligatory Charity Tax (Zakat) · Sadaqat-ul-Fitr is obligatory on the young and the old
Narrated Ibn `Umar:
حَدَّثَنَا مُسَدَّدٌ ، حَدَّثَنَا يَحْيَى ، عَنْ عُبَيْدِ اللَّهِ ، قَالَ حَدَّثَنِي نَافِعٌ ، عَنِ ابْنِ عُمَرَ ـ رضى الله عنه ـ قَالَ فَرَضَ رَسُولُ اللَّهِ صلى الله عليه وسلم صَدَقَةَ الْفِطْرِ صَاعًا مِنْ شَعِيرٍ، أَوْ صَاعًا مِنْ تَمْرٍ عَلَى الصَّغِيرِ وَالْكَبِيرِ وَالْحُرِّ وَالْمَمْلُوكِ.
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.