It is narrated from Sayyiduna Zayd bin Khalid al-Juhani (may Allah be pleased with him), the Companion of the Messenger of Allah (peace and blessings be upon him), that the Messenger of Allah (peace and blessings be upon him) said: "Jibril (peace be upon him) came to me and said: 'Say the talbiyah aloud, for it is one of the rites of Hajj.'"
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 5152