Ikrimah says that once I prayed behind Sayyiduna Abu Hurairah (may Allah be pleased with him), and whenever he would go into bowing or prostration, he would say the takbeer. I mentioned this to Sayyiduna Ibn Abbas (may Allah be pleased with them both), and Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: "Is this not the Sunnah of the Prophet (peace and blessings be upon him)?"