What is the order of priority for paying the Zakat al-Fitr (Sadaqah al-Fitr) if one only possesses enough for one Sa'?

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If an individual possesses only one Sa', they must pay it on behalf of themselves. This is established by the saying of the Prophet, peace be upon him: "Begin with yourself, then those you support." Furthermore, the obligation of Fitr is built upon the obligation of maintenance (Nafaqa), and just as one begins with oneself in maintenance, so too in Fitr.