It is narrated from Sayyiduna Khallad bin Suwayd (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Jibril (peace be upon him) came to me and said: 'O Muhammad, be one who raises his voice loudly in the Talbiyah and who sheds blood (that is, offers sacrifice).'" (The narrator explains:) "'Ajj" means raising the voice in the Talbiyah, and "thajj" means shedding blood (the blood of the sacrifice).
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6608