أَخْبَرَنَا عُبَيْدُ اللَّهِ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا يَحْيَى، عَنْ عُبَيْدِ اللَّهِ، قَالَ أَنْبَأَنَا نَافِعٌ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ كَانَ يَرْكُزُ الْحَرْبَةَ ثُمَّ يُصَلِّي إِلَيْهَا ‏.‏

Narrated Ibn Umar: It was narrated from Ibn Umar concerning the Messenger of Allah (PBUH) he said: "He used to set up a short spear then pray facing toward it." Translation Not Available

Book Ref: Sunan An Nisai Book 9 Hadith 747
Web Ref:  Sunan An Nisai Vol 1 Book 9 Hadith 748