Answered by Shaykh Amjad Rasheed
Did Imam al-Shafi`i hold that it is disliked to add “Al-Salatu khayrun min al-nawm” in the adhan of fajr in the Umm? What is the reliable position of the school? Did they contradiction their imam?
[Imam Nawawi] said in the Majmu`,
“As for the tathwib (saying of Al-Salatu khayrun min al-nawm) in the morning [s. adhan], [our school] approaches it in two ways.
The correct approach that was asserted by the author [i.e. al-Shirazi in the Muhadhdhab] and the majority of scholars is that it is definitely sunna [without any disagreement] because of the hadith of Abu Mahdhurah.
The second approach is that there are two positions regarding it [in the school]. The first position is the same as the one mentioned above [i.e., that it is sunna]. This is the position of the old school, and has been related by the judge Abu Tayyib and the author of “al-Shamil” from the text of al-Shafi`I in al-Buwaiti, which means that it has been found in the texts of the old school as well as the new school. It has also been related by the author of al-Tatimmah, from the text of al-Shafi’i, may Allah have mercy on him, from most of his books. The second position [of the second approach] is the position of the new school, which is that that it is disliked.”
As for what is said in the Umm, which is from the words of Imam al-Muzani, two rulings were related about it:
(1) the position of the old school, which is that it is sunna, and
(2) the position of the new school, which is that it is makruh.
However, you can see from the expression used in the Majmu` that the Imam, may Allah be well pleased with him, has two opinions in the new school alone. The first is that it is makruh and the second is that it is sunnah.
Actually, the second ruling [s. that it is sunna] has been related to us from the generality of the books of the Imam, so for that reason, the Imams of the madhhab have preferred it.
It is therefore clear that [the imams of the school] did not contravene their Imam, rather they gave weight to one of his positions over another one of his positions, and the position that they preferred is the position that appears in most of his books.
– Amjad Rasheed
(Translated by Shazia Ahmad)