a prohibited time, just as an unrestricted voluntary prayer is invalid if performed during the prohibited times.
The author’s statement, “If a person praying alone changes...” excludes both the congregant and the imam. Thus, the apparent meaning of the author’s words is that it is not valid for a congregant to change his obligatory prayer into a voluntary one, nor is it valid for an imam to change his obligatory prayer into a voluntary one. This is because, if the congregant were to change his obligatory prayer into a voluntary one, he would miss the congregational obligatory prayer; and congregational prayer for an obligatory prayer is mandatory. His change from an obligatory prayer to a voluntary one would therefore cause him to miss this obligation, so it is not permissible for him to change his obligatory prayer into a voluntary prayer. Likewise, if the imam changed his obligatory prayer into a voluntary one, this would mean that one offering an obligatory prayer would be following an imam offering a voluntary prayer, and for one offering an obligatory prayer to follow one offering a voluntary prayer is invalid. This would consequently invalidate the congregant’s prayer, and would thus constitute an infringement upon the rights of another.
If it is asked: Is changing an obligatory prayer into a voluntary one recommended, disliked, or neither?
The answer is that it is recommended in some cases. This is when a person begins an obligatory prayer alone and then a congregation arrives. In this situation, he has three options: either he continues his prayer and completes it as an obligatory prayer alone, without praying with the congregation that has arrived; or he interrupts it and prays with the congregation; or he changes it into a voluntary prayer and completes two rak'ahs. If he has already prayed two rak'ahs and is in the first tashahhud, he completes it and gives the salām, thereby gaining a voluntary prayer, and then joins the congregation. Here, changing from an obligatory prayer to a voluntary one is recommended in order to attain the congregation, while completing the prayer as a voluntary prayer, for if