The Prophet (ﷺ) is reported to have said, “The prayer is not valid for the one who does not recite the Fātiḥah (opening chapter) of the Book.” Reference:

Sahih Muslim 394

عَنْ عُبَادَةَ بْنِ الصَّامِتِ، يَبْلُغُ بِهِ النَّبِيَّ صلى الله عليه وسلم ‏

‏ لاَ صَلاَةَ لِمَنْ لَمْ يَقْرَأْ بِفَاتِحَةِ الْكِتَابِ ‏

‏.