Sahih Bukhari Volume 002, Book 014, Hadith Number 064.
Narated By Shu'aib : I asked Az-Zuhri, "Did the Prophet ever offer the Fear Prayer?" Az-Zuhri said, "I was told by Salim that 'Abdullah bin Umar I had said, 'I took part in a holy battle with Allah's Apostle I in Najd. We faced the enemy and arranged ourselves in rows. Then Allah's Apostle (p.b.u.h) stood up to lead the prayer and one party stood to pray with him while the other faced the enemy. Allah's Apostle (p.b.u.h) and the former party bowed and performed two prostrations. Then that party left and took the place of those who had not prayed. Allah's Apostle prayed one Raka (with the latter) and performed two prostrations and finished his prayer with Taslim. Then everyone of them bowed once and performed two prostrations individually.'"