(11) باب وُجُوبِ قِرَاءَةِ الْفَاتِحَةِ فِي كُلِّ رَكْعَةٍ وَإِنَّهُ إِذَا لَمْ يُحْسِنِ الْفَاتِحَةَ وَلاَ أَمْكَنَهُ تَعَلُّمُهَا قَرَأَ مَا تَيَسَّرَ لَهُ مِنْ غَيْرِهَا
'Ubada b. as-Samit reported from the Messenger of Allah (may peace be upon him ):
He who does not recite Fatihat al-Kitab is not credited with having observed the prayer. (ID)
Reference (ID): Sahih Muslim 394 a (ID)
In-book reference (ID): Book 4, Hadith 37 (ID)
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 771 (ID)