It is narrated from Abdullah bin Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) used to begin the recitation with 'In the name of Allah, the Most Gracious, the Most Merciful' [Surah al-Fatihah: 1].
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2398