fasting is not a condition in zakat al-fitr being obligatory on muslims. it is incumbent upon muslims even if they did not observe fast because of being aging, or ill, or traveling. furthermore, it is obligatory even on muslims who are not yet legally responsible.
on this subject we would like to cite for you the following fatwa issued by the late prominent muslim scholar, sheikh ahmad ash-sharabasi, professor of islamic creed and philosophy at al-azhar university, in which he states the following:
zakat al-fitr is incumbent on muslims in general. almighty allah says in this regard: (but those will prosper who purify themselves, and glorify the name of their guardian-lord, (and lift their hearts) in prayer.) (al-a`la 87: 14–15)
according to this verse, “purify themselves” refers to paying zakah. ibn `umar (may allah be pleased with him and his father) said, “this verse refers to the zakah of ramadan. it is meant to expiate for any mistakes or wrongdoings a person may have done during this blessed month, and it is a kind of support to satisfy the needs of the poor during the `eid.”
ibn `abbas (may allah be pleased with him and his father) also said, “the prophet (peace and blessings be upon him) enjoined zakat al-fitr so that those who fast are purified of their sins and the poor and needy people are enabled to arrange for their basic needs of food, clothing, etc. therefore, if it is paid before the `eid prayer, it will be accepted as zakat al-fitr; but if someone delays and gives it afterwards, it will be then an ordinary charity.”
this zakah is incumbent on every muslim who possesses more food than that which is not needed as a basic food for himself or his family for the duration of one day and night.
fasting is not a condition in zakat al-fitr being obligatory on muslims. an ill or old person or a traveling one who may not observe fasting is still required to pay it. besides, it is also obligatory on muslims who are not legally responsible for fasting.
muslim men are required to pay this zakah for themselves and dependents such as their wives and children. as for one’s adult sons who are financially independent, one is not required to pay for them. but if they do not work or are still students, one is then required to pay for them. as for one’s parents, one is also not required to pay this zakah for them, for one is not responsible for providing for them [unless of course they cannot provide for themselves].
ibn `umar said, “the prophet (peace and blessings be upon him) enjoined that zakat al-fitr be paid for the young and adult as well as the free and slave persons whom one is responsible for providing for.”