Bulugh al-Maram #738

Ibn ’Abbas (RAA) narrated, ‘The Messenger of Allah (ﷺ) enjoined Zakat-ul-fitr on the one who fasts (i.e. fasted during the month of Ramadan) to purify him from any indecent act or speech and for the purpose of providing food for the needy. It is accepted as Zakah for the person who pays it before the Eid prayer and it is Sadaqah (i.e. voluntary charity) for the person who pays it after the Eid prayer.’ Related by Abu Dawud and Ibn Majah and Al-Hakim graded it as Sahih.