Musnad Abi Ya'la 530 — he said: On the day of the Battle of Badr I

It is narrated from Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) that he said: "On the day of the Battle of Badr I fought fiercely. Then I came to the Prophet (peace and blessings be upon him) and saw that he (peace and blessings be upon him) was in prostration, and these words were on his blessed tongue: 'Ya Hayyu ya Qayyum' (O Ever-Living, O Sustainer of all existence!). Then I went (to the battlefield) again and fought. Then when I came back, I saw that the Prophet (peace and blessings be upon him) was still in prostration, saying the same: 'Ya Hayyu ya Qayyum' (O Ever-Living, O Sustainer of all existence!). Then Allah Almighty granted him (peace and blessings be upon him) victory and help."