Sayyiduna Anas (may Allah be pleased with him) narrates that I have offered prayers with the Prophet (peace be upon him), Sayyiduna Abu Bakr, and Umar (may Allah be pleased with them), and they did not recite « بِسْمِ اللهِ الرَّحْمٰنِ الرَّحِيْمِ » aloud.