سنن ابن ماجه

It was narrated from Ibn ‘Umar that the Messenger of Allah (ﷺ) used to set out for the praying place in the morning of the day of ‘Eid, and a small spear would be carried before him. When he reached the praying place, it would be set up in front of him, then he would pray facing it, and that was because the praying place was an open space in which there was nothing that could serve as a Sutrah*.
*Sutrah (screen), meaning a barrier of some type.