“If the regular imam commences the prayer with those whom his deputy had led, and the deputy returns to following him, it is valid.” …
The author’s statement, “If the regular imam commences the prayer with those whom his deputy had led,” apparently implies that if this occurred with someone other than the regular imam, it would not be valid. This is because the regular imam is the original imam; his leading the prayer is a return to the original arrangement, unlike anyone else. Yet the apparent view is that there is no difference if the second imam has some merit, such as better Quran recitation, greater knowledge, or greater worship. If he has no such merit, then it is not valid.
The sixth type is the transition from following an imam to leading the prayer—that is, one was a follower and then becomes an imam. It has several forms.
The first form is for the imam to appoint him as his deputy during the prayer. For example, the imam senses that his prayer will be invalidated because he feels the movement of urine and knows that it will come out. He therefore puts someone forward to complete the prayer with the congregation. The follower has thus become an imam, and this is permissible.
The second form is where two latecomers enter the prayer. One says to the other, “When the imam gives the salām, I will be your imam.” The other replies, “There is no problem.” When the imam gives the salām, one of the two becomes the other’s imam. This person has thus transitioned from following an imam to leading the prayer, while the second has transitioned from the leadership of one person to that of another.
According to the madhhab, this is permissible: there is nothing wrong with two people who entered the prayer after having missed part of it agreeing that one of them will be the imam of the other. They cited as evidence that the sunnah establishes the permissibility of transitioning from one imam to another, as in the case of Abu Bakr with the Messenger of Allah, may Allah’s blessings and peace be upon him.
Some of Imam Ahmad’s companions said that this is not permissible (1);