It wasnarrated that Ibn 'Umar said:
"A small spear (Harbah) would bebrought out to the Prophet (ﷺ) when he was travelling; he wouldplant it (in the ground) to perform prayer while facing it." (RU)
English reference (RU): Vol. 1, Book 5, Hadith 941 (RU)
Arabic reference (RU): Book 5, Hadith 994 (RU)