Our Prophet ﷺ commanded us to recite al-Fatihah and whatever else was easy.
حدثنا عبد الصمد حدثنا همام حدثنا قتادة عن أبي نضرة
أمرنا نبينا ﷺ أن نقرأ بفاتحة الكتاب وما تيسر
Its isnad is sahih, Bukhari narrated it 2/243, no. 759, in Fath al-Bari, in the Book of Adhan, chapter on recitation during Dhuhr, and Abu Dawud 1/216, no. 818, in the Book of Prayer, chapter on one who omits the recitation of the Fatihah in his prayer, and Tabarani in al-Kabir 11/238, no. 11606.