Musnad Ahmad 31:66

Sa'id ibn Mansur narrated to us, 'Abd al-'Aziz ibn Muhammad narrated to us, he said: Rabih ibn 'Abd al-Rahman ibn Abi Sa'id informed me, from his father, from Abu Sa'id al-Khudri, that the Messenger of Allah (may Allah bless him and grant him peace) sacrificed a horned ram. And he said: "This is on my behalf, and on behalf of whoever from my nation has not sacrificed."