This is Zakaat al-Fitr.

[tresbien]

With regard to the zakaah that is obligatory at the end of Ramadaan, this is Zakaat al-Fitr. The scholars are unanimously agreed that it is obligatory, except those who held odd views.

See Tarh al-Tathreeb, 4/46.

It is less important than the zakaah of wealth with regard to obligation and status. Zakaat al-Fitr is not one of the pillars of Islam, and the one who denies it is not a kaafir.

Zakaat al-Fitr was mentioned in many ahaadeeth, such as the following:

Al-Bukhaari (1503) and Muslim (984) narrated that Ibn ‘Umar (may Allaah be pleased with him) said: The Messenger of Allaah (peace and blessings of Allaah be upon him) enjoined zakaat al-fitr, a saa’ of dates, or a saa’ of barley, for every Muslim, slave or free, male or female, young or old, and he enjoined that it be given before the people go out to the prayer.
Abu Dawood (1609) narrated that Ibn ‘Abbaas said: The Messenger of Allaah (peace and blessings of Allaah be upon him) enjoined zakaat al-fitr as a purification for those who fasted from idle or obscene talk, and so as to feed the poor. Whoever gives it before the prayer, it is accepted zakaah and whoever gives it after the prayer, it is ordinary charity. Classed as hasan by al-Albaani in Saheeh Abi Dawood.