It is narrated from Sayyiduna Ubadah bin al-Samit (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "There is no prayer for the one who does not recite Surah al-Fatihah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2467