Iyas bin Salamah bin al-Akwa' narrates from his father (Sayyiduna Salamah bin al-Akwa' (may Allah be pleased with him)): We set out with Sayyiduna Abu Bakr (may Allah be pleased with him); the Messenger of Allah (peace and blessings be upon him) had appointed him as our commander in an expedition. When we drew near (the enemy), Sayyiduna Abu Bakr (may Allah be pleased with him) ordered us to halt and camp. When we had prayed the dawn prayer, Sayyiduna Abu Bakr (may Allah be pleased with him) ordered an attack on all sides. We came upon the watering place and killed whom we killed.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18235