Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.087.

Zakat ul-fitr is a type of sadaqah which must be paid by every Muslim, young and old, male and female, free and slave, at the end of the month of fasting (Ramadan).

Al-Bukhari and Muslim relate from Ibn ‘Umar that he said: “The Prophet, upon whom be peace, enjoined the payment of one sa’ of dates or one sa’ of barley as zakat ul-fitr on every Muslim, young and old, male and female, free and slave.”