This is surat Al-fatiha, the greatest surah in the Qur`an. Allah chose it to be repeated seventeen time per day in the prayer and about double this if a person prayed the sunnan. The prayer will not be expectable without it according to the hadith reported by Imams Bukhari and Muslim what the prophet Muhammad (S.A.W.) said: `There is no prayer for whom do not read the Fatiha.` (more)