Musnad Ahmad 27:1284

Aswad ibn Amir narrated to us, Harim informed us, from Ubayd Allah, from Nafi’, from Ibn Umar, who said: "The Messenger of Allah (ﷺ) used to carry the *‘anzah* (a short spear) with him during the two Eids and on his travels. It would be planted in the ground in front of him, and he would pray facing it."