I Samuel - Chapter 30
You Know That Rashi in Parshas VaYishlach...?
Arriving home to Ziklag, David and his men discovered that the Amalekites had attacked in their absence. They burned the city and took all the women and children captive. (Miraculously, they didn't kill anybody, quite counter to their usual modus operandi.) David's wives Achinoam and Avigayil were also among the captives. The people were so upset, they were ready to stone David for leading them away with Achish, leaving their own city undefended. David asked Aviasar the Kohein (Priest) to consult G-d as to whether they should pursue and if they would be victorious; G-d said yes on both counts.
While pursuing the Amalekites, David's men found an Egyptian man starving in the field. He was the slave of an Amalekite who had become ill three days earlier, so they left him behind, with neither food nor water. He agreed to lead David to his former masters.
David and his men found the Amalekites partying and enjoying their booty. The Jewish army handily defeated them, except for 400 soldiers who fled on camels. (These 400 youths were descendants of the 400 men who deserted Esau rather than attack Jacob in Genesis chapter 33. They were spared as a reward for that - see Rashi on Gen. 33:16.) All the captives were recovered, safe and sound.
400 of David's men had gone to battle; 200 remained behind, guarding the gear. Some of the 400 didn't want to share the spoils with the non-combatants, but David wouldn't have it. Not only did he give equal shares to the 200 who stayed back on guard, he also sent gifts as a sign of gratitude to the towns that had supported them in the tough times.