Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) narrates: On the day of the Battle of Badr I took some part in the fighting, then I came hurrying to see what the Prophet (peace and blessings be upon him) was doing. The Prophet (peace and blessings be upon him) was in prostration, reciting: 'Ya Hayyu ya Qayyum, ya Hayyu ya Qayyum' (O Ever-Living, O Self-Sustaining; O Ever-Living, O Self-Sustaining), and he was not saying anything more than this. I went back to the fighting; then when I came, I found him in prostration, reciting the same words. Then I went back to the fighting, and when I came, he was still reciting this, until Allah Almighty granted him victory.
Al-Bazzar recorded it, and its chain is hasan (good); Abu Ya'la recorded a similar report in the same way.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأدعية / 17197