Scholars have disagreed about the basmalah:
a) Some had the opinion that the basmalah is an aayah in every Soorah of the Qur’aan, so based on this, Soorah Al-Kawthar consists of four aayahs.
b) Some had the opinion that it is not an aayah in any Soorah of the Qur’aan.
c) Some had the opinion that it is one aayah which was revealed to separate the Soorahs.
d) Al-Shaafi’y had the opinion that it was of Soorah Al-Faatihah.
However, scholars are unanimous that it is not an aayah at the beginning of Soorah A-Tawbah and that it is part of a an aayah in Soorah AN-Naml. The difference in opinion is for other than this. Among the strongest proofs for the opinion that it is or is not an aayah, is reporting consensus on the opinion of either side. Each party reported a consensus, and rely upon this:
a) Those who had the opinion that it is an aayah used a proof, saying that the companions were in consensus upon writing it in the Qur’aan book, and if it was not an aayah, they would not have dared to enter it into the Qur’aan book.
b) Those who had the opinion that it is not an aayah used consensus as their proof, saying that had it been an aayah, it would not have been permissible to differ about it. Indeed, if a person disagrees about a letter of the Qur’aan upon which there is consensus, scholars deem this to be disbelief, because the Qur’aan is preserved against addition or omission.
c) Others who had the opinion that it is an aayah which was revealed to separate the Soorahs which takes them out of the above types of consensus. This opinion is the one which is deemed soundest by Shaykh Al-Islaam (may Allaah’s Mercy be upon him) and a group of scholars. It also appears that this is the strongest opinion.