One who is too weak to fast

Qatadah narrates: Sayyiduna Anas (may Allah be pleased with him) became unable to fast; this was a year before his death. So he stopped fasting, and for each day he would feed one needy person.
Al-Tabarani recorded it in al-Mu'jam al-Kabir, and its narrators are the narrators of the Sahih.

Ayyub bin Abi Tamimah narrates: Sayyiduna Anas (may Allah be pleased with him) became unable to fast, so he had a large bowl of tharid prepared, invited thirty needy people and fed them.
Abu Ya'la recorded it, and its narrators are the narrators of the Sahih.

Mujahid narrates: Qays bin al-Sa'ib grew so old that he reached one hundred and sixty years of age, and he became unable to fast, so food would be given on his behalf.

In one narration the wording is: I heard Sayyiduna Qays bin al-Sa'ib (may Allah be pleased with him) say: In the month of Ramadan a person may pay a ransom (fidyah) by feeding one needy person for each of its days, so on my behalf give one needy person a sa' of food for each day. The Prophet (peace and blessings be upon him) was my business partner in the Days of Ignorance, and he was the best of partners; he would neither dispute nor quarrel in buying and selling.
Al-Tabarani recorded it in al-Mu'jam al-Kabir, and its narrators are thiqat (trustworthy).