RobH_en_tn/1sa/29/04.md

He will not go down with us into battle

The person here is a synecdoche for the army he commands. Alternate translation: "Do not let his army join with our army against our enemies" (See: rc://en/ta/man/translate/figs-synecdoche)

For how else could he make himself acceptable to his master than by taking the heads of our own men?

This rhetorical question can be translated as a statement. Here "taking the heads" is a metonym for killing. Alternate translation: "The best way for David to make peace with his master would be by killing our soldiers!" (See: rc://en/ta/man/translate/figs-rquestion and rc://en/ta/man/translate/figs-metonymy)