Musnad Ahmad 1063:1

Waki’ narrated to us, Hisham bin Sa’d narrated to us, from Zayd bin Aslam, from ‘Abd al-Rahman bin ‘Ata’, from a group of the Banu Salamah, who said: The Prophet, peace and blessings of Allah be upon him, was sitting, and he tore his garment. He said: "I have appointed a time for a sacrificial animal to be marked today."