Abu Hurairah (may Allah be pleased with him) narrates that the Messenger of Allah (peace be upon him) said: "Jibreel (peace be upon him) ordered me to recite the Talbiyah aloud because it is one of the symbols of Hajj." Imam Abu Bakr (may Allah have mercy on him) says that I have mentioned the chains of this hadith in Kitab al-Kabir.