Wiki,

"Thou shalt not kill (LXX; οὐ φονεύσεις), You shall not murder (Hebrew לֹא תִּרְצָח lo tirṣaḥ) or You shall not kill (KJV), is a moral imperative included as one of the Ten Commandments in the Torah,[1] specifically Exodus 20:13 and Deuteronomy 5:17.

The imperative is against unlawful killing resulting in bloodguilt.[2] The Hebrew Bible contains numerous prohibitions against unlawful killing, but also allows for justified killing in the context of warfare, capital punishment, and self-defense."

The New Testament is in agreement that murder is a grave moral evil,[44] and maintains the Old Testament view of bloodguilt.[45] Jesus himself repeats and expands upon the commandment, "Do not murder."[46] The New Testament depicts Jesus as explaining that murder, as well as other sins, comes from the heart.

For out of the heart come evil thoughts, murder, adultery, sexual immorality, theft, false testimony, slander.

— Matthew 15:19 (NIV)
The New Testament acknowledges the just and proper role of civil government in maintaining justice[47] and punishing evildoers, even to the point of "bearing the sword."[48]

Like the Old Testament, the New Testament seems to depict the lawful use of force by soldiers in legitimate battles as justified.[53] The profession of soldier is used as a metaphor by Paul exhorting the Ephesians to "put on the full armor of God."[54] Cornelius, the Roman centurion, is portrayed as a righteous and God-fearing man.[55] Jesus praises the faith of a Roman centurion on the occasion of healing the centurion's servant, and states that he has not found such great faith even in Israel.[56] When John the Baptist was preaching repentance and baptizing penitent sinners in the Jordan river, soldiers came to John and asked for specific instructions regarding their repentance. John the Baptist did not demand that the soldiers renounce their profession, instead he exhorted them to be content with their pay.