A spear used to be brought out for the Prophet ﷺ during travel, and he would plant it in the ground and pray facing it.
حدثنا محمد بن الصباح أنبأنا عبد الله بن رجاء المكي عن عبيد الله عن نافع
كان النبي ﷺ تخرج له حربة في السفر فينصبها فيصلي إليها
No references are available.
Bukhari related it in the Book of Prayer, Chapter on the Screen of the Imam Being a Screen for Those Behind Him, hadith no. 494, and Muslim related it in the Book of Prayer, Chapter on the Screen of One Praying and the Recommendation of Praying Toward a Screen, etc., hadith no. 501, from the hadith of Abdullah bin Ibn Umar, in its longer form.