ʿUyūn Akhbār al-Ridha & al-‘Āmāli: ibn Bābawayh again, in a mursal fashion, who said:

It was said to ‘Amīr al-Mu’minīn عليه السلام: Oh ‘Amīr al-Mu’minīn, inform us about ‘In the name of Allāh, The Entirely Merciful, The Especially Merciful (Bismillah al-Raḥmān al-Raḥīm)’, is it from the Opening of the Book (i.e. al-Fātiḥa)?
He replied: Yes, The Messenger of Allāh used to recite it and consider it a part of al-Fātiḥa, and he would say: “The Opening of the Book1 is the seven repeated verses.”

1. The Opening of the Book (Fātiḥat al-Kitāb) is named as such – according to some scholars – because it was the first complete Chapter (Ṣurah) revealed to The Messenger of Allāh صلى الله عليه وآله. Another reasons the scholars posit, is that it is due to it being the first Chapter (Ṣurah) of the Qur’ān.

ابن بابويه أيضا مرسلا ، قال : قيل لأمير المؤمنين ( عليه السلام ) : يا أمير المؤمنين ، أخبرنا عن * ( بِسْمِ اللَّه الرَّحْمنِ الرَّحِيمِ ) * أهي من فاتحة الكتاب ؟ فقال : نعم ، كان رسول الله ( صلى الله عليه وآله ) يقرأها ويعدها منها ، ويقول : فاتحة الكتاب هي السبع المثاني