(90) باب سُتْرَةُ الإِمَامِ سُتْرَةُ مَنْ خَلْفَهُ
Narrated Ibn `Umar:
Whenever Allah's Messenger (ﷺ) came out on `Id day, he used to order that a Harba [??] (a short spear) to be planted in front of him (as a Sutra for his prayer) and then he used to pray facing it with the people behind him and used to do the same while on a journey. After the Prophet (ﷺ) , this practice was adopted by the Muslim rulers (who followed his traditions).
Reference: Sahih al-Bukhari 494
In-book reference: Book 8, Hadith 141
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 1, Book 9, Hadith 473