عن ابن عباس قال: كان النبي صلى الله عليه وسلم لا يعرف فصل السورة حتى تنزل عليه {بسم الله الرحمن الرحيم}.
[صحيح] - [رواه أبو داود]
المزيــد ...
Ibn ‘Abbās (may Allah be pleased with him) reported: The Prophet (may Allah’s peace and blessings be upon him) did not know where Surahs were to be separated until "In the name of Allah, the Most Compassionate, the Most Merciful" was revealed to him.
Sahih/Authentic. - [Abu Dawood]
The Prophet (may Allah’s peace and blessings be upon him) did not know where Surahs should be separated until the basmalah (in the name of Allah, the Most Compassionate, the Most Merciful) was revealed to him. In other words, when the basmalah was sent down, he would know that a Surah came to an end and a new one was being revealed. The basmalah is a verse that was revealed like the other verses. But, we may not read it at the beginning of Surat at-Tawbah, by analogy with the other Surahs. Also, if we begin the recitation from any place within a Surah, we are recommended not to say basmalah, according to this Hadīth, for the verse of basmalah was sent down at the beginning of Surahs. Some scholars disagree with this view, however.