What does 1 Samuel 5:3 mean?

When the Philistines first heard the Israelites had brought the ark of the covenant (Exodus 25:10–16) to the battlefield, they were terrified. They heard how the God of the Israelites brought plagues on Egypt. How could they fight against such a god (1 Samuel 4:6–8)? Their assumption was that the physical object—the ark, itself—channeled the power of Israel's deity. The Israelites brought the ark into battle under a similar superstition. Soon, though, that misunderstanding was dissolved. The Philistines thoroughly defeated the Israelites, crushing their army and sending survivors running for their lives. They even captured the ark as a trophy in the end (1 Samuel 4:9–11).

Now they have brought the ark back home to Ashdod and put it in the temple of their own god, Dagon. This was meant to show that Dagon had beaten Yahweh, Israel's God, in battle. Perhaps they meant to humiliate Yahweh and the Israelites by making it appear that Yahweh had come to Dagon's temple to worship their god as superior.

When the Philistines enter the temple the next morning, though, they find something startling. The large statue of Dagon has fallen. It is lying face down on the ground in front of the ark of the covenant. In that position, it appears as if Dagon is lying prostrate in an attitude of worship and adoration before Israel's God. They quickly set the Dagon statue back up where it normally stood, but it would not remain there.