The Various Stages of Fasting & Fidyah (Hadith No. 1665)

Bismillah.
Volume 3, Book 31, Number 170:
Narrated Nafi:
Ibn 'Umar (radiallaahu `anhu) recited the verse: "They had a choice either to fast or to feed a poor person for every day, and said that the order of this Verse was cancelled.
This ayah is 184 of Surah al-Baqarah:
Fast for a fixed number of days, but if any of you is ill or on a journey, the same number (should be made up) from other days. And as for those who can fast with difficulty, (e.g., an old man), they have (a choice either to fast or) to feed a Miskin (poor person) (for every day). But whoever does good of his own accord, it is better for him. And that you fast is better for you if only you know.
In the Tafsir, Ibn Kathir says:

The Various Stages of Fasting

Al-Bukhari and Muslim recorded that `A'ishah said, "(The day of) `Ashura' was a day of fasting. When the obligation to fast Ramadan was revealed, those who wished fasted, and those who wished did not.'' Al-Bukhari recorded the same from Ibn `Umar and Ibn Mas`ud.
Allah said:

﴿وَعَلَى الَّذِينَ يُطِيقُونَهُ فِدْيَةٌ طَعَامُ مِسْكِينٍ﴾

(...those who can fast with difficulty, (e.g., an old man), they have (a choice either to fast or) to feed a Miskin (poor person) (for every day).)
Mu`adh commented, "In the beginning, those who wished, fasted and those who wished, did not fast and fed a poor person for each day.'' Al- Bukhari recorded Salamah bin Al-Akwa` saying that when the Ayah:

﴿وَعَلَى الَّذِينَ يُطِيقُونَهُ فِدْيَةٌ طَعَامُ مِسْكِينٍ﴾

(...those who can fast with difficulty, (e.g., an old man), they have (a choice either to fast or) to feed a Miskin (poor person) (for every day).) was revealed, those who did not wish to fast, used to pay the Fidyah (feeding a poor person for each day they did not fast) until the following Ayah (2:185) was revealed abrogating the previous Ayah. It was also reported from `Ubaydullah from Nafi` that Ibn `Umar said; "It was abrogated.'' As-Suddi reported that Murrah narrated that `Abdullah said about this Ayah:

﴿وَعَلَى الَّذِينَ يُطِيقُونَهُ فِدْيَةٌ طَعَامُ مِسْكِينٍ﴾

(those who can fast with difficulty, (e.g., an old man), they have (a choice either to fast or) to feed a Miskin (poor person) (for every day).) "It means `those who find it difficult (to fast).' Formerly, those who wished, fasted and those who wished, did not but fed a poor person instead.'' Allah then said:

﴿فَمَن تَطَوَّعَ خَيْرًا﴾

(But whoever does good of his own accord) meaning whoever fed an extra poor person,

﴿فَهُوَ خَيْرٌ لَّهُ وَأَن تَصُومُواْ خَيْرٌ لَّكُمْ﴾

(it is better for him. And that you fast is better for you) Later the Ayah:

﴿فَمَن شَهِدَ مِنكُمُ الشَّهْرَ فَلْيَصُمْهُ﴾

(So whoever of you sights (the crescent on the first night of) the month (of Ramadan, i.e., is present at his home), he must observe Sawm (fasting) that month) (2:185) was revealed and this abrogated the previous Ayah (2:184).

The Fidyah (Expiation) for breaking the Fast is for the Old and the Ailing

Al-Bukhari reported that `Ata heard Ibn `Abbas recite:

﴿وَعَلَى الَّذِينَ يُطِيقُونَهُ فِدْيَةٌ طَعَامُ مِسْكِينٍ﴾

(And as for those who can fast with difficulty, (e.g., an old man), they have (a choice either to fast or) to feed a Miskin (poor person) (for every day).)
Ibn `Abbas then commented, "(This Ayah) was not abrogated, it is for the old man and the old woman who are able to fast with difficulty, but choose instead to feed a poor person for every day (they do not fast).'' Others reported that Sa`id bin Jubayr mentioned this from Ibn `Abbas. So the abrogation here applies to the healthy person, who is not traveling and who has to fast, as Allah said:

﴿فَمَن شَهِدَ مِنكُمُ الشَّهْرَ فَلْيَصُمْهُ﴾

(So whoever of you sights (the crescent on the first night of) the month (of Ramadan, i.e., is present at his home), he must observe Sawm (fasting) that month.) (2:185)
As for the old man (and woman) who cannot fast, he is allowed to abstain from fasting and does not have to fast another day instead, because he is not likely to improve and be able to fast other days. So he is required to pay a Fidyah for every day missed. This is the opinion of Ibn `Abbas and several others among the Salaf who read the Ayah:

﴿وَعَلَى الَّذِينَ يُطِيقُونَهُ﴾

(And as for those who can fast with difficulty, (e.g., an old man)) to mean those who find it difficult to fast as Ibn Mas`ud stated. This is also the opinion of Al-Bukhari who said, "As for the old man (person) who cannot fast, (he should do like) Anas who, for one or two years after he became old fed some bread and meat to a poor person for each day he did not fast.''
This point, which Al-Bukhari attributed to Anas without a chain of narrators, was collected with a continuous chain of narrators by Abu Ya`la Mawsuli in his Musnad, that Ayyub bin Abu Tamimah said; "Anas could no longer fast. So he made a plate of Tharid (broth, bread and meat) and invited thirty poor persons and fed them.'' The same ruling applies for the pregnant and breast-feeding women if they fear for themselves or their children or fetuses. In this case, they pay the Fidyah and do not have to fast other days in place of the days that they missed.

Taken from: http://ilookilisten.wordpress.com/2013/08/15/the-various-stages-of-fasting-fidyah-hadith-no-1665/