«إذا قرأتم {الْحَمْدُ لِلَّهِ} فاقرءوا {بِسْمِ اللَّهِ الرَّحْمَنِ الرَّحِيمِ} إنها أم القرآن وأم الكتاب والسبع المثاني و {بِسْمِ اللَّهِ الرَّحْمَنِ الرَّحِيمِ} إحدى آياتها»
The Prophet (peace and blessings be upon him) said:
"When you recite Alhamdu lillah, then also recite Bismillahir-Rahmanir-Rahim, for it (Surah al-Fatihah) is Umm al-Qur'an, Umm al-Kitab and the seven oft-repeated verses (al-Sab' al-Mathani), and Bismillahir-Rahmanir-Rahim is one of its verses."
Hadith Referenceصحیح الجامع الصغیر / حرف الألف / 729