It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him): I prayed behind Abu Bakr, Umar bin al-Khattab and Uthman (may Allah be pleased with them). All of them, when they began the prayer, did not recite 'Bismillah al-Rahman al-Rahim' (In the name of Allah, the Most Gracious, the Most Merciful).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2418