The reasoning is that this prayer mat stands in for its owner and takes his place. Just as you may not make a man leave his place and then sit in it yourself, likewise you may not remove his prayer mat.
What the author’s words imply is that a person may lay down a prayer mat and reserve the place, for if laying down the mat and reserving the place were forbidden, it would be obligatory to remove the mat and to denounce the wrong. Since the author grants the prayer mat inviolability, this indicates that laying it down is permissible. This is the established position of the madhhab.
However, the sound view in this matter is that reserving a place and then leaving the mosque is not permissible, and that one may remove the prayer mat that has been laid out, because the principle is: “Whatever is put in place without right may rightfully be removed.” But if removing it is feared to lead to harm, such as hostility, resentment, or the like, then it should not be removed, for warding off harms takes precedence over procuring benefits. If Allah knows from your intention that, were it not for this laid-out prayer mat, you would have occupied that place, then Allah may reward you with the reward of those who arrived early, since you only left this foremost place due to an excuse.
His statement, “unless the prayer is about to begin,” means that when the prayer begins with the iqamah, we may remove it, because at that point it has no inviolability. Moreover, if we were to leave it, there would be a gap in the row, which is contrary to the sunnah. But may we pray on it without removing it?
The answer is: We may not pray on it without removing it, because it is someone else’s property, and we may not make use of another person’s property without his permission. Rather, we should remove it.
Issue: An exception is made from the stronger view that laying down a prayer mat is forbidden: