حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم فَرَضَ زَكَاةَ الْفِطْرِ مِنْ رَمَضَانَ عَلَى النَّاسِ صَاعًا مِنْ تَمْرٍ أَوْ صَاعًا مِنْ شَعِيرٍ عَلَى كُلِّ حُرٍّ أَوْ عَبْدٍ ذَكَرٍ أَوْ أُنْثَى مِنَ الْمُسْلِمِينَ ‏.‏

Yahya related to me from Malik from Nafi from Abdullah ibn Umarthat the Messenger of Allah, may Allah bless him and grant him peace,made the zakat of breaking the fast at the end of Ramadan obligatoryon every muslim, whether freeman or slave, male or female, andstipulated it as a sa' of dates or a sa' of barley. Translation Not Available

Book Ref: Muwatta Imam Malik Book 17 Hadith 629
Web Ref:  Muwatta Imam Malik Book 17 Hadith 53