An example of giving preference to another in a recommended matter is giving him preference regarding a virtuous place, such as giving someone else preference in the first row. The most that can be said about this is that it is disliked, or contrary to what is preferable.
An example of giving preference to another in a permissible matter is to give someone food that one desires but is not in need of. This is commendable, for Allah praised the Ansar, saying:
“They give preference to others over themselves, even though they are in need.”
His statement, “but not accepting it,” means that accepting such preference is not disliked. Thus, if you say to someone, “Come forward and take my place in the first row,” it is not disliked for him to accept and move forward.
His statement, “No one other than the one giving preference may precede him,” means that it is not lawful for anyone other than the one being given preference to precede the one giving preference—that is, to take precedence over the person whom he has given preference.
For example, if Zayd gives Amr preference in his place, but Bakr gets there before him, this is not lawful for Bakr, because Zayd gave preference only to Amr.
More serious than this is what some people do when they arrive and find the row complete: they pull someone out of the row, causing the person pulled back to step back so that he may stand in a row with him, while the newcomer moves forward into his place. This may lead to the invalidity of the prayer of the person who was pulled back. Moreover, he had done you a kindness by stepping back to stand with you, yet you repay him with this mistreatment.
It is forbidden to remove a laid-out prayer mat before the time for prayer has arrived.
His statement, “It is forbidden to remove a laid-out prayer mat before the time for prayer has arrived,” means that it is forbidden to remove the prayer mat that its owner has put down in order to pray upon and then left. A prayer mat is something upon which one prays, such as a rug.
The scenario is that a man places his prayer rug in the row and then leaves the mosque. It is not permissible for you to remove this prayer mat.