I'm familiar with battles where a undisciplined army, after winning a partial victory and stopping to plunder, gets attacked by reformed or held-back enemies (Tagliacozzo 1268, Mezőkeresztes 1596), but are there any cases where the prospect of plunder was used to intentionally lull an enemy into dispersing and plundering, and then springing the trap?
Herodotus writes in his Histories how Cyrus the Great raised a massive banquet and left it guarded by only a few men as he performed battlefield maneuvers. 1/3 of Tomyris's army split off to capture it. They were all killed.
Tomyris would go on to win the battle, however. She supposedly dipped Cyrus's head in a skin full of blood to make good on her threat to give him his fill of it.
Edit: corrected an inaccuracy about the fate of Cyrus's skull.
In 200 CE Yuan Shao sent his commander Wen Chou and 5,000 cavalry to pursue the retreating warlord Cao Cao across the yellow river. Cao Cao, deciding to stand and fight, ordered all but 600 of his most elite cavalry to dismount and release their horses. Wen Chou's formation broke ranks to claim the riderless horses and in this moment Cao Cao ordered his 600 to attack, pushing them back across the river and killing Wen Chou in the process.
EDIT: Corrected date