Volume 5 · Book 59 · Hadith 320
Narrated Usaid: On the day of Badr, Allah's Apostle said to us, "When the enemy comes near to you, shoot at them but use your arrows sparingly (so that your arrows should not be wasted)."
— Sahih Bukhari, Volume 5, Book 59: Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi), Hadith #320