Explanation
The author—may Allah have mercy on him—quotes from ʿĀʾishah (Allah be pleased with her) that the Messenger of Allah ﷺ said, “When any one of you becomes drowsy while praying, let him lie down until the sleepiness passes.”

Nuʿās (drowsiness) is a temporary numbness of the senses caused by sleep overcoming a person so that he can no longer control them. For this reason the Prophet ﷺ directed anyone overpowered by drowsiness during the prayer to break off the prayer altogether and not continue in that state. He then explained why: when someone prays while drowsy, he is unaware of what he is saying; he may intend to seek forgiveness but end up cursing himself. Instead of saying, “O Allah, forgive me my sin,” he might actually revile himself for the very sin from which he seeks pardon. Likewise, he might wish to ask Allah for Paradise but inadvertently ask for the Fire, or hope to request guidance yet ask his Lord for misguidance. Therefore the Prophet ﷺ ordered him to lie down.

One of the lessons here is that a person’s own self has a right over him. If he forces himself to worship while it entails undue hardship, he has wronged himself. Brother, do not be negligent and fall short, nor excessive and go to extremes.

The hadith thus teaches that a person should not burden himself or impose hardship upon himself in worship; rather, he should undertake only what he can realistically manage. And Allah alone grants success.