The Old Testament always considered blood a sacred sign of life. 60 This teaching remains necessary for all time.
Catechism number 2262
In the Sermon on the Mount, the Lord recalls the commandment, "You shall not kill,"62 and adds to it the proscription of anger, hatred, and vengeance. Going further, Christ asks his disciples to turn the other cheek, to love their enemies.63 He did not defend himself and told Peter to leave his sword in its sheath.64
Legitimate defense