Then they said, "What shall be the trespass-offering which we shall return to him?" They said, "Five golden tumors, 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.
"After he had made sport of them"  (1 Samuel 6:6).  The diviners clearly recommended sending the ark back after the first plague instead of waiting for ten plagues.  The subject of this clause is God, the meaning being that God, in truth, had made sport (or mockery) of the Egyptians throughout ten plagues; and, of course, the Egyptians finally let the people go.  Like many other figures in the Bible, this is an anthropomorphism, portraying God as a strong man laughing and making fun of some weak and bungling enemy.