Sunan Ibn Majah — Establishing the Prayer and the Sunnah Regarding Them — Hadith No: 1305
Translation
It was narrated that Ibn ‘Umar said:“When the Prophet (ﷺ) prayed on the day of ‘Eid or on another occasion, a small spear was set up in front of him, and he prayed facing it, and the people were behind him.” Nafi` said: It is from here that the leaders have taken this practice