Several of our companions from Ahmad b. Muhammad b. Khalid from `Ali b. al-Hakam from Aban al-Ahmar from Hamza b. at-Tayyar from Abu `Abdillah عليه السلام. He said: Write. So he dictated to me: From our saying is that Allah obligated the servants by what He has given them and what He has made them recognize. Then, He sent a messenger to them and revealed to them a Book, in which He commanded and prohibited. Therein, he ordered them to perform salat and fast. The Messenger of Allah صلى الله عليه وآله slept upon salat, so Allah said, “I make you sleep and I make you wake. When you wake up, pray, so that they may learn what to do if that were to happen to them”. It is not the way that they say, “If one slept upon it (i.e. the time of prayer) he is destroyed”. And it is like that with fasting, “I cause you to become ill and I give you good health, so if I gave you health, then compensate for it (i.e. the missed fast)”.
Then, Abu `Abdillah عليه السلام said: And it is like that if you look into all things – no one has been constricted, and no one [will be held accountable] except that there is a proof for Allah upon him, and therein is Allah’s wish. And I do not say, “They can do whatever they wish”. He then said: Allah guides and sets astray. And he said: They are not ordered to do what they are not capable of. And the people are capable of doing all of the things that He has ordered them to do. And all things that they are incapable of doing have been exempted from them. However, there is no good in the [disbelieving] people. He عليه السلام then recited: “There is no blame on those who are infirm, or ill, or who find no resources to spend” (9:91) – so He exempted them – “…no ground can there be against such as do right: and Allah is the Forgiving, the Merciful. Nor (is there blame) on those who came to you to be provided with mounts” (9:91-92). He said: So he exempted them because they do not have the means.