Sahih al-Bukhari 3985
Book 64: Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi) · Narrated by Abu Usaid
Arabic
حَدَّثَنِي مُحَمَّدُ بْنُ عَبْدِ الرَّحِيمِ، حَدَّثَنَا أَبُو أَحْمَدَ الزُّبَيْرِيُّ، حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ الْغَسِيلِ، عَنْ حَمْزَةَ بْنِ أَبِي أُسَيْدٍ، وَالْمُنْذِرِ بْنِ أَبِي أُسَيْدٍ، عَنْ أَبِي أُسَيْدٍ ـ رضى الله عنه ـ قَالَ قَالَ لَنَا رَسُولُ اللَّهِ صلى الله عليه وسلم يَوْمَ بَدْرٍ " إِذَا أَكْثَبُوكُمْ ـ يَعْنِي كَثَرُوكُمْ ـ فَارْمُوهُمْ، وَاسْتَبْقُوا نَبْلَكُمْ ".
English translation
Narrated Abu Usaid:On the day of (the battle of) Badr, Allah's Messenger (ﷺ) said to us, "When your enemy comes near to you (i.e. overcomes you by sheer number), shoot at them but use your arrows sparingly
Reference: Sahih al-Bukhari 3985, Book of Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi). English translation by Dr. Muhammad Muhsin Khan.