Musannaf Ibn Abi Shayba 3:5883

Abu Bakr narrated to us, he said: Jarir ibn Abd al-Hamid narrated to us, from Ata, from Sa’id ibn Jubayr and Abu al-Bakhtari—he said: I think he included their companions—they said: When the two armies meet and the people strike one another, and the time for prayer arrives, then say: "Subhan Allah, wal-hamdu lillah, wa la ilaha illallah, wallahu akbar" (Glory be to Allah, and praise be to Allah, and there is no god but Allah, and Allah is the Greatest). That is your prayer, then do not repeat it.