Sunan Ibn Majah 1305
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.
حَدَّثَنَا سُوَيْدُ بْنُ سَعِيدٍ، حَدَّثَنَا عَلِيُّ بْنُ مُسْهِرٍ، عَنْ عُبَيْدِ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ كَانَ النَّبِيُّ ـ صلى الله عليه وسلم ـ إِذَا صَلَّى يَوْمَ عِيدٍ أَوْ غَيْرَهُ نُصِبَتِ الْحَرْبَةُ بَيْنَ يَدَيْهِ فَيُصَلِّي إِلَيْهَا وَالنَّاسُ مِنْ خَلْفِهِ ‏.‏ قَالَ نَافِعٌ فَمِنْ ثَمَّ اتَّخَذَهَا الأُمَرَاءُ ‏.‏