It Is Obligatory To Recite Al-Fatihah In Every Rak'ah; If A Person Cannot Recite Al-Fatihah Or Cannot Learn It, Then He Should Recite Whatever Else He Can Manage — Sahih Muslim 396 a

The Messenger of Allah (ﷺ) said: One is not credited with having observed the prayer without the recitation (of al-Fatiha). So said Abu Huraira: (The prayer in which) the Messenger of Allah (ﷺ) recited in a loud voice, we also recited that loudly for you (and the prayer in which) he recited inwardly we also recited inwardly for you (to give you a practical example of the prayer of the Holy Prophet).