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)."
Vol: 005 Book: 059 Hadith: 320
A Selected Dua
With you, those who are fasting have broken their fast, you have fed those who are righteous, and the angels recite their prayers upon you.
Info: Abu Dawud 3/367, Ibn Majah 1/556, An-Nasa'i, 'Amalul-Yawm wal-Laylah 296-8. Al-Albani graded it authentic in Sahih Abu Dawud 2/730.