It is narrated from Ikrimah that Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: "The Messenger of Allah (peace and blessings be upon him) prayed two rak'ahs, and in them he recited nothing except Surah al-Fatihah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2469