1 Samuel 6:4
Then said they, What shall be the trespass offering which we shall return to him? They answered, Five golden emerods, and five golden mice, according to the number of the lords of the Philistines: for one plague was on you all, and on your lords.
The question put was what trespass or guilt offering should be returned to Israel's God. The answer prescribed by the Philistine priests and lords was five golden emerods or tumors and five golden mice, one pair for each of the five lords. The number five was matched to the number of lords because one plague was upon all, upon both the people and their rulers.
The golden images represented the plagues and afflictions suffered, following a heathen custom of offering a figure of the disease or of the affected body part in hope of warding it off or removing it. The plague included a fatal disease shown by the tumors and an infestation of mice that damaged the crops and food supply of the land. The mice represented that infestation that damaged the food supply of the land.
The offering was a costly gift sent back with the ark to honor Israel's God, in hope that He would accept it and heal them and relieve the affliction. By this offering the Philistines acknowledged that God's hand was upon them and recognized that the presence of the ark, which belonged to Israel, was the cause of their affliction.