“Those who are heedless of their prayer” [al-Ma'un 107:5]—that is, they are inattentive to it: they do not care about it or establish it properly. They remain aware of what they are doing, unlike one who forgets something within his prayer, for he is not aware of what he has done.

Some scholars said: “Praise be to Allah, who said, ‘heedless of their prayer,’ and did not say, ‘heedless within their prayer.’”

What is meant here is forgetfulness in the prayer.

Forgetfulness in prayer occurred to the Prophet, peace and blessings be upon him, because it is inherent to human nature. Thus, when he forgot something in his prayer, he said: “I am only a human being like you: I forget as you forget. So when I forget, remind me.” (1) It is part of human nature, and it does not mean that a person is turning away from the prayer. For we are certain that the person who established the prayer most perfectly was the Messenger, peace and blessings be upon him; yet forgetfulness occurred to him.

The kinds of forgetfulness mentioned in the sunnah are: addition, omission, and doubt. All of them occurred to the Prophet, peace and blessings be upon him.

It is prescribed for an addition, an omission, or doubt, …

His statement, “It is prescribed for an addition, an omission, or doubt”: “It is prescribed” means that it is obligatory in some cases and recommended in others.

“For an addition”: the lām denotes causation—that is, because of an addition, an omission, or doubt. This applies generally, not in every individual case, since it will be explained that for some additions, omissions, and doubts, prostration is not prescribed. Therefore, we say that it is prescribed for an addition; that is, the reason for its legislation is addition, omission, and doubt,