Contradiction with Exodus 20:13
This verse states "Thou shalt not kill," which contradicts the theme of warfare and killing surrounding the interactions between Saul and David.
Exodus 20:13: Thou shalt not kill.
Contradiction with Mathew 5:44
This verse advises to "love your enemies," contrasting with the hostility between Saul and David.
Contradiction with Proverbs 25:21
Advises feeding your enemy if he is hungry, conflicting with the ongoing enmity depicted in 1 Samuel 26.
Proverbs 25:21: If thine enemy be hungry, give him bread to eat; and if he be thirsty, give him water to drink: