The Statement of Allah "[Observing Saum (fasts)] 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, etc.) 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." (V.2:184)

وَقَالَ عَطَاءٌ يُفْطِرُ مِنَ الْمَرَضِ كُلِّهِ كَمَا قَالَ اللَّهُ تَعَالَى‏.‏ وَقَالَ الْحَسَنُ وَإِبْرَاهِيمُ فِي الْمُرْضِعِ وَالْحَامِلِ إِذَا خَافَتَا عَلَى أَنْفُسِهِمَا أَوْ وَلَدِهِمَا تُفْطِرَانِ ثُمَّ تَقْضِيَانِ‏.‏ وَأَمَّا الشَّيْخُ الْكَبِيرُ إِذَا لَمْ يُطِقِ الصِّيَامَ، فَقَدْ أَطْعَمَ أَنَسٌ بَعْدَ مَا كَبِرَ عَامًا أَوْ عَامَيْنِ كُلَّ يَوْمٍ مِسْكِينًا خُبْزًا وَلَحْمًا وَأَفْطَرَ‏.‏ قِرَاءَةُ الْعَامَّةِ ‏{‏يُطِيقُونَهُ‏}‏ وَهْوَ أَكْثَرُ‏.‏Ata said, "One may stop fasting if one is suffering from any kind of disease, as Allah تعالى says concerning nursing or pregnant women." Al-Hasan and Ibrahim said, "If they are afraid of harming themselves or their babies, they can give up fasting for the time being and make up for the missed fasts later on. If an old man has no strength to observe fast (he can feed a poor person daily). When Anas bin Malik became old, he used to provide a poor person with bread and meat everyday while he gave up fasting during the last one or two years of his life."