1 Samuel 5:4
2 The Philistines took the ark of God and brought it into the temple of Dagon, where they positioned it beside Dagon. 3 When the residents of Ashdod got up early the next day, Dagon was lying on the ground before the ark of the Lord. So they took Dagon and set him back in his place. 4 But when they got up early the following day, Dagon was again lying on the ground before the ark of the Lord. The head of Dagon and his two hands were sheared off and were lying at the threshold. Only Dagon’s body was left intact.
1 Samuel 17:51
50 David prevailed over the Philistine with just the sling and the stone. He struck down the Philistine and killed him. David did not even have a sword in his hand. 51 David ran and stood over the Philistine. He grabbed Goliath’s sword, drew it from its sheath, and after killing him, he cut off his head with it. When the Philistines saw their champion was dead, they ran away. 52 Then the men of Israel and Judah charged forward, shouting a battle cry. They chased the Philistines to the valley and to the very gates of Ekron. The Philistine corpses lay fallen along the Shaaraim road to Gath and Ekron.
Notes and References
"... Scholars routinely link Goliath’s death to Dagon’s destruction. God caused Dagon to fall facedown to the ground (1 Samuel 5:3). After the Philistines set their god aright, God caused Dagon to fall again. This time, the Lord decapitated Dagon. Similarly, after falling facedown to the ground in 17:49, David decapitated Goliath (verse 51). Goliath’s death certainly echoes Dagon’s. Surely one reason the narrative says that Goliath fell facedown was to create a link with Dagon’s demise. The Lord defeated the Philistines’ champion just as he previously defeated their god ..."
Verrett, Brian A. The Serpent in Samuel: A Messianic Motif (p. 157) Resource Publications, 2020