Silsilat al-Ahadith al-Sahihah

Abu Hurairah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "When you recite «الْحَمْدُ لِلَّـهِ» (i.e., Surah Al-Fatihah), then recite «بِسْمِ اللَّـهِ الرَّحْمَـٰنِ الرَّحِيمِ», because this Surah is Umm al-Qur'an, Umm al-Kitab, and Sab‘ al-Mathani (i.e., the seven oft-repeated verses), and «بِسْمِ اللَّـهِ الرَّحْمَـٰنِ الرَّحِيمِ» is one of its verses."