Quoting Commentary for I Samuel 5:7

כי לא כצורנו צורם, “for their Rock is not like our Rock;” besides they know that our G–d is not like any of their deities, as when the Jewish people observed the covenant they had entered into with their G–d, they had been unable to harm them in any way. Not only that; during those eras their G–d had dealt harshly with them and their so-called deities. A prime example is found in Samuel I 5,7, after the Philistines had captured the Holy Ark, first their deity Dagon was found lying on its face in front of the Holy Ark. After picking it up in its former place the same thing happened on the second morning. By that time this idol had lost its hands and its legs, only the trunk remaining intact. The citizens of Ashdod became struck with hemorrhoids, and decided to rid themselves at all costs of the Holy Ark. They attributed their problems to the G–d of Israel, and instead of enjoying their victory over the army of the Israelites considered themselves as having become the victims. They should have realised that if the Jewish G–d had punished His own people, He would deal even more harshly with those who victimised His people. From here on in Moses expounds on what will be the fate of our perennial enemies.