Narrator:Abdullāh ibn ‘Umar
وَعَن ابْن عمر أَنَّ عُمَرَ بَعَثَ جَيْشًا وَأَمَّرَ عَلَيْهِمْ رَجُلًا يُدْعَى سَارِيَةَ فَبَيْنَمَا عُمَرُ يَخْطُبُ فَجَعَلَ يَصِيحُ: يَا أَمِيرَ الْمُؤْمِنِينَ لَقِيَنَا عَدُوُّنَا فَهَزَمُونَا فَإِذَا بِصَائِحٍ يَصِيحُ: يَا سَارِيَ الْجَبَلَ. فَأَسْنَدْنَا ظُهُورَنَا إِلَى الْجَبَلِ فَهَزَمَهُمُ اللَّهُ تَعَالَى رَوَاهُ الْبَيْهَقِيُّ فِي دَلَائِل النُّبُوَّة
Ibn `Umar told that 'Umar sent off an army over which he appointed a man called Sariya as commander. While `Umar was addressing the people he began to shout, `Keep near the mountain, Sari[*]" A messenger came later from the army and said, "Commander of the faithful, we met our enemy and they routed us, then someone began to shout, `Keep near the mountain, Sari,' so we set our backs to the mountain and God most high routed them." *A shortened form of the man's name. Baihaqi transmitted it in Dala'il an-nubuwa.
Cited in Mishkat al-Masabih (No. 5954).