Contradiction with Exodus 13:17
This verse explains that God did not lead the Israelites through the land of the Philistines, which could imply a differing interaction compared to making peace in Genesis 21:23.
Exodus 13:17: And it came to pass, when Pharaoh had let the people go, that God led them not [through] the way of the land of the Philistines, although that [was] near; for God said, Lest peradventure the people repent when they see war, and they return to Egypt:
Contradiction with 1 Samuel 17:1
This verse describes the Philistines gathering for war against Israel, suggesting hostility rather than the peace treaty mentioned in Genesis 21:23.
1 Samuel 17:1: Now the Philistines gathered together their armies to battle, and were gathered together at Shochoh, which [belongeth] to Judah, and pitched between Shochoh and Azekah, in Ephesdammim. [Ephesdammim: or, the coast of Dammim, called Pasdammim]
Contradiction with Judges 3:3-4
These verses state that certain nations, including the Philistines, were left to test Israel, which contrasts with the peaceful coexistence implied in Genesis 21:23.
Judges 3:3-4: [Namely], five lords of the Philistines, and all the Canaanites, and the Sidonians, and the Hivites that dwelt in mount Lebanon, from mount Baalhermon unto the entering in of Hamath.
Contradiction with 1 Samuel 4:2
This verse shows the Philistines defeating Israel in battle, indicating conflict contrary to the agreement in Genesis 21:23.
1 Samuel 4:2: And the Philistines put themselves in array against Israel: and when they joined battle, Israel was smitten before the Philistines: and they slew of the army in the field about four thousand men. [they joined...: Heb. the battle was spread] [army: Heb. array]
Contradiction with Judges 14:4
It describes the Philistine domination over Israel, which goes against the idea of a peaceful oath between parties in Genesis 21:23.
Judges 14:4: But his father and his mother knew not that it [was] of the LORD, that he sought an occasion against the Philistines: for at that time the Philistines had dominion over Israel.