Jabir bin Abdullah says that in the Battle of Dhat-ur-Ruqa' the Holy Prophet (SAW) asked his companions to rest for the night on a plain surrounded by the mountains."  "Who will volunteer to guard us tonight?" The Holy Prophet (SAW) asked.

        Immediately, two companions, namely Ammar bin Yathir and Abbad bin Bishr came forward and volunteered to stand guard while the army of Islam slept.

        As they stationed themselves at a strategic spot on the terrain, Abbad said: "Let us divide the night, I shall keep the vigil in the first half, and you in the second."  So Ammar slept while Abbad remained vigilant, engaged in nightly prayers.  In the middle of his prayers, an enemy soldier stealthily came near and shot an arrow which hit Abbad.  He pulled out the arrow and continued his prayers.  Another arrow hit him causing a further injury.  Abbad pulled it out again and remained steadfast.  When the third arrow wounded him further, Abbad hastily bowed down in prostration to complete his prayers.  He awakened Ammar and related to him what had transpired.

        Ammar began to tend his wounds and wipe off blood from his body, then asked: "Why did you not wake me when you were first hit?"

        Abbad said: "I was in my prayers, and I did not feel like abandoning my communion with Allah.  When I felt terribly weakened by the third blow, I bowed down to complete my prayers.  Had it not been for the Holy Prophet's (SAW) order to stand guard, I would not have disturbed your sleep."

Reference:
Pearls of Wisdom.  A String of Incidents in the History of Islam.  The World Federation of Khoja Shia Ithna-Asheri Muslim Communities. Page 17