Contradiction with Exodus 20:3
This verse commands worship of no other gods, contradicting 1 Samuel 5:3, where the image of Dagon is of significance to the Philistines.
Exodus 20:3: Thou shalt have no other gods before me.
Contradiction with Isaiah 42:8
This verse states that God will not give His glory to another or His praise to idols, contradicting the reverence shown to Dagon's statue in 1 Samuel 5:3.
Isaiah 42:8: I [am] the LORD: that [is] my name: and my glory will I not give to another, neither my praise to graven images.
Contradiction with Jeremiah 10:5
This verse describes idols as powerless and unable to move on their own, contrasting with the movement of the idol in 1 Samuel 5:3.
Jeremiah 10:5: They [are] upright as the palm tree, but speak not: they must needs be borne, because they cannot go. Be not afraid of them; for they cannot do evil, neither also [is it] in them to do good.
Contradiction with Psalm 115:4-7
These verses talk about the impotency of idols, contradicting the implied presence and power of Dagon in the 1 Samuel 5:3 narrative.
Psalm 115:4-7: Their idols [are] silver and gold, the work of men's hands.
Contradiction with Deuteronomy 12:3
This verse commands the destruction of pagan gods' images, which contrasts with the continued presence of Dagon's statue in 1 Samuel 5:3.
Deuteronomy 12:3: And ye shall overthrow their altars, and break their pillars, and burn their groves with fire; and ye shall hew down the graven images of their gods, and destroy the names of them out of that place. [overthrow: Heb. break down]