Musnad Ahmad 337:10

I read to Abd al-Rahman ibn Mahdi: Malik. And Rawh narrated to us, he said: Malik—meaning Ibn Anas—narrated to us, from Abdullah ibn Abi Bakr ibn Muhammad ibn Amr ibn Hazm, from Abd al-Malik ibn Abi Bakr ibn Abd al-Rahman ibn al-Harith ibn Hisham, from Khallad ibn al-Sa'ib al-Ansari, from his father, that the Messenger of Allah, peace and blessings of Allah be upon him, said: "Gabriel, peace be upon him, came to me and said: 'Command my companions, or those who are with me, to raise their voices in the Talbiyah, or in the Ihlal.'" He meant one of the two.