ENOfficial
It was narrated that Ibn ‘Umar said: “A small spear (Harbah) would be brought out to the Prophet (ﷺ) when he was travelling; he would plant it (in the ground) to perform prayer while facing it.”
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُحَمَّدُ بْنُ الصَّبَّاحِ، أَنْبَأَنَا عَبْدُ اللَّهِ بْنُ رَجَاءٍ الْمَكِّيُّ، عَنْ عُبَيْدِ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ كَانَ النَّبِيُّ ـ صلى الله عليه وسلم ـ تُخْرَجُ لَهُ حَرْبَةٌ فِي السَّفَرِ، فَيَنْصِبُهَا فَيُصَلِّي إِلَيْهَا .
sunnah.com