Musnad Ahmad 27:1859

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from Ayyub, from Nafi', from Ibn 'Umar: "The Prophet, may Allah bless him and grant him peace, used to take out the 'Anzah (a short spear) with him on the day of Fitr and Adha, so that he would plant it in the ground, and pray facing it."