The first is illustrated by Allah’s words:

“Pilgrimage to the House is a duty owed to Allah by those who are able to make their way to it.” [Āl ‘Imrān: 97]

And by the Prophet’s words (may Allah bless him and grant him peace) to ‘Imrān ibn Husayn:

“Pray standing; if you cannot, then sitting; and if you cannot, then lying on your side.”

It is well known that pilgrimage and prayer are obligatory upon those who have the capacity to perform them, whether they actually perform them or not. Thus, this capacity need not coincide with the act.

The second is illustrated by Allah’s words:

“They were unable to hear, nor could they see.” [Hūd: 20]

And His words:

“On that Day We shall display Hell plainly before the disbelievers * whose eyes were veiled from My remembrance and who were unable to hear.” [al-Kahf: 101-102]

This is according to those who interpret capacity here in this second sense.

According to the interpretation of the early Muslim generations and the majority, however, their inability means that this is burdensome for them and difficult for their souls. Their souls cannot bring themselves to will it, although they could do it if they so willed. Such is the condition of someone whose desires or erroneous views prevent him from listening to Allah’s revealed Books and following them; it has been stated that he is unable to do so.

This is the capacity that accompanies the act and necessarily entails its occurrence. As for the first kind, without it no obligation would apply, as in His words: