Explanation of the author's statement: "It is obligatory for every Muslim who has a surplus on the day of the festival and its night to give a sa' (a dry measure of about 3 kg) in excess of his own food, the food of his dependents, and his basic needs."

The Shaykh : He said, "It is obligatory for every Muslim". The verb "obligatory" refers to zakat al-fitr. His statement "for every Muslim" excludes those who are not Muslim, such as a Jew, a Christian, an idolater, or others, so zakat is not obligatory upon them. This is based on the hadith of Ibn 'Umar and because zakat is a purification, and a disbeliever is not worthy of purification except through Islam; nothing purifies him but Islam.
The apparent meaning of the author's words is that even if a person is a slave to someone who is a disbeliever, zakat al-fitr is not obligatory on his behalf, and this is indeed the case. "A sa' (a dry measure of about 3 kg) remained for him on the day of the festival and its night" means that he has, on the day of the festival and its night—namely, the night of the festival—a sa' (a dry measure of about 3 kg) in excess. These two are in the accusative case as adverbs of time. The word "sa' (a dry measure of about 3 kg)" is the subject of "remained." The sa' (a dry measure of about 3 kg) was specified as the obligatory amount because it is the required amount; a person is not obligated to give more than a sa' (a dry measure of about 3 kg), nor is the amount less than a sa' (a dry measure of about 3 kg) sufficient to discharge the obligation, but rather one must give what is within his capacity.
"In excess of his own food and the food of his dependents". "His own food" means his food and drink. "The food of his dependents" is likewise. "And his basic needs" are those things whose presence in the house is required by necessity, for there is a distinction between necessity, need, and surplus.
Necessity is well known. Need is what the house requires to be present, and perfection is what is not required to be present. If a sa' (a dry measure of about 3 kg) remains after his basic needs, and a fortiori after his necessities, then zakat al-fitr becomes obligatory upon him, because this is the amount prescribed by the Shari'ah.
He said, "And debt does not prevent it, except if he seeks it". Yes. We also benefit from the author's (may Allah have mercy on him) statement "for every Muslim who has a surplus..." in that he mentioned the first condition, which is Islam, and the second condition, which is wealth in the manner he described, namely that he has on the day of the festival and its night a sa' (a dry measure of about 3 kg) in excess of his own food, the food of his dependents, and his basic needs. The apparent meaning of the author's words is that if these two conditions are met, it becomes obligatory, even if he did not fast Ramadan. For example, if an elderly person is unable to fast, he still pays zakat al-fitr. The evidence for this is the hadith of Ibn 'Umar . The term "young child" includes even one in the cradle, who does not fast, so this includes every Muslim, whether he fasted or not. What about a woman in post-natal bleeding who gives birth on the first day of Ramadan and continues bleeding until the tenth of Shawwal, so that the entire month passes without her fasting? Is zakat al-fitr obligatory upon her? She is a Muslim and has more than her own food, the food of her dependents, and her basic needs.